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re 

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es 


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d'images  n6cessaire.  Les  diagrammes  suivants 
illustrent  la  m6thode. 


errata 
1  to 


e  pelure, 
on  d 


n 

32X 


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6 

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Ai 


^ 


PROSPECTING 


FOR 


GOLD  AND  SILVER. 


BY 

Arthur  Lakes, 

/// 

Late  Professor  of  Geology  at  the  State  School  oj  Mines, 
Golden  City,  Colorado. 

Author  of  "Gi'.OLOGY  OF  Colorado  and  Western  Ore  Deposits," 
"Geoi.oc.y  of  Colorado  Coal  Deposits,"  Etc. 


■    »  ^  m   t 


SCRANTON,   PA. 
THE   COLLIERY  ENGINEER   CO 

1896. 


583575 

1(.  5-.  54 


Entered  according  to  the  Act  of  Congress  in  the  Year  1895, 

By  The  Colliekv  Engineer  Co., 
In  the  Office  of  the  Librarian  of  Congress,  at  Washington 


'" 


1 


PREFACE. 


\ 


I 


In  preparing  this  little  work  the  author  has  felt  the 
difficulty  which  arises  in  a  theoretical  dissertation  on  scv 
eminently  practical  a  subject  as  prospecting.  It  seems  like 
giving  rules  and  prescriptions  for  hunting  or  fishing  or  any 
other  natural  or  practical  pursuit.  Though  theory  and 
practice  are  not  at  variance  when  happily  combined,  yet. 
either  without  the  other  proves  very  unsatisfactory.  Tnus- 
the  reader  of  this  book,  should  he  start  out  armed  only  with 
its  theory,  will  find  himself  for  some  time  pretty  much 
"  at  sea  "  when  he  comes  to  actual  practice  in  the  field.  As,. 
however,  he  gradually  obtains  some  practical  experience,  he 
may  find  this  little  work  of  use  to  him.  So,  also,  the 
seasoned  prospector,  who  has  hitherto  trusted  to  luck,  keen- 
ness of  observation,  intuition  and  experience,  may  find  him- 
self in  the  future  much  better  equipped  by  acquiring  a  little 
of  the  theory. 

Whilst  we  have  endeavored  to  give  the  prospector  all 
assistance  in  our  power,  as  to  {he  best  means  of  educating 
himself,  describing  his  outfit,  etc.,  we  have  devoted  special 
attention  to  the  description  of  such  geological  and  other  phe- 
nomena as  he  is  likely  to  meet  with  in  connection  with  his 
work,  so  that  he  may  have  an  intelligent  idea  of  them  when 
he  encounters  them. 

We  have  selected  just  as  much  material  as  we  think  would 
be  most  interesting  and  useful  to  him,  saving  him  the  time 
and  trouble  of  wading  through  heavy  tomes  and  laboriously" 
picking  out  from  a  vast  amount  of,  for  his  purpose,  super- 
fluous matter,  that  which  he  will  most  require. 

The  work  is  intended  to  be  a  popular  one,  addressed  to 
the  average  student,  prospector  and  miner  and  to  the 
general  public.  The  illustrations  are  largely  drawn  by  the 
author  from  Colorado  mines  and  Rocky  Mountain  subjects 
which  are  most  familiar  to  him. 


ARTHUR   LAKES, 

State  School  of  Mines, 

Golden  Citv,  Colorado. 


January  i,  1895. 


CONTENTS 


CHAPTER  ^^'^^ 

I.     On  Prospecting— Preparation  and  Outfif  for  Work 7 

II.     The  Prospector's  Historical  Geology 24 

III.  The  Prospector's  Paleontology  or  Study  of  Fossils 36 

IV.  The  Prospector's  Lithology  or  Study  of  Rocks.- 47 

V.     The  Prospector's  Mineralogy 59 

VI.     Ore  Deposits— Theories  Regarding  the  Origin  of  Ore 

Deposits 67 

VII.     Various  Forms  of  Ore  Deposits 83 

VIII.     Relation  of  Veins  to  Eruptive  Forces 93 

IX.     Gold  Placers --  104 

X.     Deep  Leads.. m 

XI.     Mining  Regions— Showing  Examples  of  Ore  Deposits..  117 

XII.     Ore  Deposits  in  Sedimentary  Rocks 151 

XIII.  Examining  and  Sampling  Mining  Properties,  Prospects 

or  Mines ^74 

XIV.  SaltingMines 1S5 

XV.     Prospectors'  Tools,  and   How  to  Sharpen  and  Temper 

Them -. - ---  192 

XVI.     Some  Elements  of  Mining  Law  Relating  to  Prospecting.  200 


iJlM 


chaptp:r  I. 


ON   PROSPECTING— PREPARATION   AND   OUTFIT 

FOR  WORK. 

The  regular  prcjsnector,  as  a  rule,  has  at  some  time  of  his 
checquererl  career  had  some  actual  experience  in  the  mines 
themselves,  from  which  he  has  learned  by  observation,  the 
appearance  of  different  ores,  their  different  values,  how  the 
veins  appear  on  the  surface,  h(JW  to  open  a  vein,  and  the 
uses  of  pick,  shcn'cl,  and  blasting  powder.  In  a  word  he  is 
a  miner,  who  has  become  too  restless  to  stick  to  steady 
work,  and  so  follows  the  more  uncertain  and  precarious 
livelihood  of  seeking  for  new  and  undiscovered  veins,  many 
of  which  even  in  an  old  mining  district  may  yet  be  dis- 
covered covered  up  by  brush  or  debris,  whilst  a  new  district 
offers  a  most  enticing  field.  These  mineral  veins  or  ledges, 
may  make  him  in  a  moment  a  comparatively  rich  man,  and  if 
he  finds  them,  they  will  cost  him  nothing,  only  a  simple  com- 

f)liance  with  the  inexpensive  regulations  of  the  law.  So  the 
ife  of  a  prospector  offers  many  attractions  to  one  who  is 
restless  and  loves  to  roam  and  loves  to  find  something  new 
and  is  not  afraid  of  considerable  hardship.  To  save  a  vast 
amount  of  time  and  labor,  he  should  acquire  knowledge. 
Thus,  for  instance,  if  he  were  prospecting  for  coal  he  would 
be  wasting  his  time  in  hunting  for  it  in  granite,  or  if  he  was 
hunting  for  the  precious  metals,  he  would  lose  time  in 
looking  for  them  among  the  unaltered  sedimentary  strata  of 
the  prairie.  This  is  merely  for  example,  but  an  infinite 
variety  of  knowledge  is  necessary  for  him  in  his  vocation, 
besides  even  that  of  the  simpler  elements  of  geology,  such 
as  the  knowledge  of  different  kinds  of  minerals,  and  their 
value,  the  kind  of  places  and  peculiar  rocks  they  are 
associated  with,  their  appearance  on  the  surface,  etc.,  etc. 


8 


to^'cther  with  some   knowledge  of  assaying  or  blowpiping 
or  panning. 

In  a  newly  rlisccjvered  camp,  men  will  rush  in  lor  a  lew 
weeks,  work' a  little  in  the  dinerent  mines,  suflkient  to  give 
them  an  idea  of  the  kind  of  ores  and  rocks  and  other 
circumstances  in  the  locality,  and  then  will  strike  out  on 
their  own  account  and  prospect  around  the  camp  for  new 
veins  or  extensions  of  those  already  discovered.  An 
extension,  by  th.e  way,  of  a  very  rich  discovered  lode  is  n<jt 
always  to  be  relied  on.  Nature  seems  often  to  concentrate 
her  riches  at  one  point,  and  leave  the  extension  barren,  as 
in  the  case  of  the  Comstock  of  Ne\'ada.  liut  little  wealth 
has  been  found  outside  of  the  great  lode  and  mine  itself. 

The  best  education  is  in  the  mines  themselves,  so  a 
novice  on  arriving  at  a  mining  region  had  better  spend  as 
much  time  as  possible  in  practical  work.  in.  and  around  the 
various  mines,  before  he  launches  out  prospecting.  A 
prospector  can  rarely  carry  about  much  assaying  or  other 
apparatus  with  him  tor  determining  the  character  or  value 
of  ores  he  may  find,  and  hence  it  is  well  for  him  to  accustom 
himself  to  these  ores  in  the  mines  themselves.  Also  he 
should  acquaint  himself  with  the  peculiar  ores  of  each 
particular  district,  before  he  attempts  to  prospect  in  its 
vicinity,  for  an  ore  such  as  coarse  grained  galena,  in  one 
district  may  be  generally  rich,  whilst  in  another  it  is 
remarkably  poor  in  silver. 

The  best  previous  education  for  a  prospector  would  be  a 
course  at  a  school  of  mines,  where  he  will  learn  the 
elements  of  geology,  mineralogy,  assaying,  etc.  And  next 
to  that,  practical  work  in  the  mines  tJiemselves,  and  lastly 
the  prospecting  field,  A  little  knowledge  of  blowpiping 
may  also  help  him,  which  he  may  acquire  at  his  school. 

Having  left  his  school,  he  should  learn  the  practical  use 
of  the  pick,  drill,  and,  blasting  powder.  By  working  annind 
a  concentrator  he  will  learn  tne  nifference  between  ore  and 
gangue  rock;  and  "picking"  or  "sorting"  ores,  will  teach 
him  at  sight  the  values  of  ores.  The  prospector  shc^uld 
know  how  to  open  his  vein  or  ledge,  when  he  finds  it.  with 
pick,  shovel,  and  blasting  apparatus,  A  little  carpentry 
will  teach  him  how  to  make  a  handwinch,  and  a  few  lessons 
in  blacksmithing,  will  teach  him  how  to  sharpen  and 
temper  his  tools,  for  there  will  probably  be  no  blacksmith's 
shop  or  carpenter's  either,  within  miles  of  where  he  may  go. 
Other  prospectors  will  teach  him  how  to  use  his  pan  or 
iron  spoon  for  testing  ores,  and  various  other  dodges  and 


make-shifts.  An  important  point  is  to  learn  how  to  average 
approximately  the  <iiiantity  of  ore  in,  and  value  of,  a  ler'ge 
when  he  has  found  one.  V'aluahle  ore  on  a  ledge  lies  in 
pockets,  strings,  bunches,  irregularly  distributed  throdgh 
the  (|uart/  or  other  material  ol  the  vein  ;  he  should  leai  n  t<j 
tell  at  sight  the  relative  proportion  of  ore  and  gangUw.  He 
would  do  well  to  study  the  result  oi  working  ores  in  a  mill 
or  furnace,  such  as  trying  to  estimate  the  yield  of  bullion  of 
the  ores  which  are  mined,  taking  them  in  weekly  or 
monthly  lots.  With  some  such  preliminary  knowledge  he 
is  ready  for  the  held. 

HIS  ouTi'ir. 

The  following  list  (jf  necessaries  by  Mr.  A.  Balch  in  his 
"Treatise  on  Mining"  is  as  full  as  can  be  given  by  any  one, 
and  is  more  than  the  average  prospector  generally  needs. 


A  PROSPECTOR   AND    HIS   OUTFIT. 

"First,  Two  pairs  of  heavy  blankets  weighing  about  8 
pounds  each. 

Second.    A  buffalo  robe  or  a  blanket  lined  poncho. 

Third.  Suit  of  strong  gray  wo<  len  clothes,  pair  of  brown 
jean  trousers,  a  change  of  wool  m  underclcUiing,  woolen 
socks,  pair  o^     eavy  boots,  soft  felt  hat,  three  or  four  large 


f 


Id 

colored  handkerchiefs,  a  pair  of  buckskin  gauntlets,  toilet 
articles,  etc.    All  should  go  into  a  strong  canvas  bag. 

Fourth.  A  breech  loading  rifle  or  shot  gun  and  a  revolver. 
Around  hi's  waist  a  strong  sash  to  carry  his  holster  and 
knife,  in  a  sheath.  His  ammunition,  if  his  revolver  is  large 
bore,  may  conveniently  fit  both  his  rifle  and  revolver. 
Pipe  and  tobacco. 

Fifth.  A  sure  footed  native  or  mountain  pony.  A 
Mexican  saddle  with  its  saddle  horn,  straps,  etc.,  to  tie  on 
various  things,  such  as  his  pack,  bags,  water  canteen,  etc. 
The  left  stirrup  may  be  fitted  with  a  leather  tube,  in  which 
the  rifle  barrel  may  be  placed.  A  strap  around  the  saddle 
horn  will  secure  the  gun  stock.    The  long  lariat  or  stake 


t^^y^ 


A   PROSPECTOR  S  TOOLS. 


I,  2.  Picks. 

3.  L(    g  handled  Shovel. 
4,  5.  Drills. 

6.  Heavy  Hammer. 

7.  Blasting  Powder. 


8.  Pan. 

9.  Horn  Spoon. 

10.  Iron  Spoon. 

11.  Fuse. 


rope  for  tethering  his  horse  should  be  coiled  up  and  tied  bj- 
a  strap  to  the  saddle  horn. 

Sixth.  For  prospecting,  a  '  poll '  pick  and  prospecting 
pan  made  of  iron  or  a  horn  spoon  should  be  carried.  The 
pan  is  also  useful  besides  for  washing  out  sand,  as  a  dish 
or  bathing  vessel.  A  large  iron  spoon  for  melting  certain 
metals  is  likewise  to  be  carried,  and  in  some  cases  a  small 
portable  Battersea  assaying  furnace. 

.Seventh.  A  frying  pan  8  inches  diameter  of  wrought  iron, 
a  coffee  pot,  tin  cup,  spoon,  and  fork,  and  matches  in  tin 
box,  pocket  compass,  a  spy  glass,  or  pair  of  field  glasses. 


n 

Eighth.  Provisions,  bacon,  flour,  beans,  coffee,  or  tea, 
pepper,  salt,  and  box  of  yeast  powder,  all  packed  in  strong 
bags,  to  go  into  a  canvas  sack.  A  few  lessons  in  the  kitchen 
on  cooking  will  be  advantageous  before  starting. 

Ninth.  Packing  the  bronco.  Place  a  folded  blanket  on 
the  horse's  back,  on  this  lay  the  saddle.  The  saddle  ba^-s 
contain  small  things.  The  bags  with  provisions  are  placed 
behind  the  cantle  of  the  saddle;  on  top  of  this  the  bag  of 
clothing.  The  pick  goes  on  top  tied  by  a  thong.  Coffee 
pot,  and  frying  pan  are  lashed  on  the  bags." 

Sometimes  a  prospector  takes  a  horse  to  ride  on  and 
another  as  a  pack  animal,  or  a  donkey  only.  For  grass  and 
water  for  his  horse,  he  must  trust  to  the  country.  He  will 
fix  his  temporary  camp  in  some  suitable  location,  where 
these  are  to  be  found,  and  thence,  as  from  headquarters, 
prospect  daily  the  adjacent  country  returning  nightly,  it 
may  be,  to  his  camp. 


BRIEF  SKETCH    OF    PROSPECTING. 

We  may  divide  the,  prospecting  for  the  precious  metals 
into  two  general  classes:  hunting  for  gold  in  gold  placers; 
hunting  for  gold  and  silver  bearing  ledges  or  veins  or 
deposits. 

"Placers"  are  places  where  gold  having  been  torn  from 
the  ledges  and  rocks  by  denudation,  b)-^  water  and  ice,  is 
swept  down  by  these  agencies  till  it  finally  finds  a  resting 
place.  Gold  being  heavier  than  quartz  or  country  rock, 
sinks  to  the  bottom  first.  If  the  stream  is  violent,  it  will 
carry  the  gold  on,  if  fine,  till  it  comes  to  an  eddy  or  pool, 
where  the  waters  are  more  quiet,  and  there  it  will  sink.  The 
water  carries  the  clay  and  lighter  stones  still  further  on.  In 
this  way  millions  of  tons  of  rocks  containing  more  or  less 
gold  disseminated  through  them  may  have  been  reduced, 
and  the  gold  set  free,  or  the  gold  may  have  been  derived 
from  a  few  individual  gold  bearing  ledges  or  veins. 

The  prospector  takes  his  pick,  shovel  and  pan,  and  his 
horn  spoon,  and  finds  perhaps  an  old  dry  river  bed  where 
the  water  has  ages  ago  receded.  At  some  point  the  sides  of 
this  old  river  course  widen  out  suddenly,  forming  a  basin. 
"Here,"  says  the  prospector,  "there  must  have  been  an 
eddy,"  and  he  prospects  it  accordingly;  at  another  point  he 
finds  a  place  where  the  water  must  have  run  over  a  rock, 
and  made  a  waterfall;  at  the  bottom  he  digs  again. 

He  loosens  the  soil  with  his  pick,  and  shovels  it  out;  at  a 


■w 


12 


certain  depth,  which  may  be  from  5  to  20  feet  or  more,  he 
strikes  "bed  rock,"  which  may  be  granite,  shale,  sandstone, 
or  some  other  rock.  Here  he  looks  for  nuggets,  and  with 
his  knife  digs  into  all  the  little  crevices  of  the  rock  to  hunt 
for  them  and  for  scales  and  wires  of  gold. 


PANNING  GOLD   AT   CRIPPLE  CREEK,   COLORADO. 

Also  whilst  sinking  his  shaft,  he  pans  the  gravel  carefull)" 
at  various  depths,  especially  where  there  are  streaks  of  clay 
or  "black  sand."  The  latter  are  grains  or  little  pebbles  of 
magnetic  iron  ore,  acomnif/u  accompaniment  of  gold,  altered 


i 


13 

relics  of  the  iron  pyrites  in  which  the  gold  was  originally 
contained. 

He  fills  his  pan  half  full  of  water,  throws  into  it  a  shovel- 
full  of  dirt,  first  picking  out  the  pebbles,  stirs  the  mass 
with  his  lingers  till  the  water  is  fully  charged  with  the  rlay 
and  gradually  winnows  out  all  the  clay.  Filling  the  pan 
again  with  water,  he  gives  it  a  peculiar  circular  motion  and 
each  little  wave  of  sand  passes  off  till  the  whole  is  winnowed 
ofi,  and  at  last  he  sees  specks  of  gold  shining  free  in  the 
bottom  of  the  pan.  Then  it  is  not  difficult  to  estimate 
approximately  the  amount  of  gold  to  the  bushel  or  ci.bic 


FINDING   THE   FLOAT, 

foot  of  earth  of  the  placer,  and  thus  to  estimate  the  approx- 
imate value  of  the  placer.  He  then  locates  or  stakes  out 
his  placer  claim  according  to  the  regulations  of  the  U.  S. 
Government,  which,  by  a  single  individual  cannot  exceed 
twenty  acres. 

The  second  class  of  prospectors  are  those  who  try  to  dis- 
cover ore  deposits,  ledges  or  veins,  "  in  place,"  that  is,  in  the 
hard  rocks  of  the  hills. 

The  prospector's  first  effort  is  to  finr'  "float."  A  vein 
outcropping  on  the  surface,  becomes  oxidized  and  crumbles 
by  action  of  the  atmosphere,  rain,  etc.;  pieces  break  off  and 
fall  down  hill.     Some  of  this  float  is  barren  quartz  or  country 


'm0m 


14 

rock,  others  may  be  mineralized.  Commonly  "  float  "  is  a 
rustv,  spongy  mass  of  rock,  showing  besides  iron  often  some 
copper  stains,  and  in  it  there  may  be  grains  of  galena, 
pyrite  or  some  other  ore.  He  tries  'to  trace  this  "  float  "  to 
its  home  in  the  ledge  whence  it  came.  Of  one  thing  he  is 
certain,  the  "float"  must  have  rolled  i^own  and  not  «/  hill. 
If  the  "float"  is  fairly  scattered  over  the  lower  zone  of  the 
hill,  and  no  "float"  is  found  above  that  zone,  on  the  top  of 
that  zone  he  will  hunt  for  his  ledge.  If  the  "float  "is  all 
over  the  hill  he  assumes  the  ledge  is  on  the  top. 

If  he  finds  his  "  float"  at  the  mouth  of  a  canyon  or  water 
course,  he  walks  up  that  water  course,  noticing  not  only  the 
"  float,  "  and  its  diminishmg  or  increase,  but  also  any  pecu- 
liar rocky  pebbles,  such  as  a  peculiar  porphyry,  perhaps, 
which  he  may  by  chance  recognize  again  further  up  in 
place,  and  give  him  a  hint  as  to  whence  the  stream  derived 
most  of  its  material  of  pebbles.  He  notices  if  the  "  float," 
fragments  increase  as  he  proceeds,  and  whether  they  sud- 
denly cease  at  a  certain  point;  at  that  point  he  hunts  for  the 
ledge  on  either  side  of  the  canyon,  and  breaks  off  any  pieces 
that  may  look  likely. 

Having  found  the  ledge  and  traced  its  croppings,  he  tries 
to  find  out  its  approximate  value.  This  he  does  by  break- 
ing off  at  intervals  along  it  likely  looking  fragments  of  the 
rock,  grinding  them  up  to  about  the  size  of  peas.  He 
mixes  these  well,  and  takes  a  half  of  them,  reducing  this  to 
fine  powder,  and  again  halving  it,  till  of  the  whole  ledge  he 
•can  carry  awaj^  an  averaged  sample  of  a  few  ounces.  He 
may  wash  this  in  his  pan  to  see  if  there  is  any  free  gold  in  it; 
other  ores  he  will  recognize  at  sight.  These  samples  he 
will  have  assayed  and  the  returns  will  show  the  approximate 
value.  He  measures  the  length  and  thickness  of  the  vein, 
und  examines  the  wall  enclosing  it. 

He  then  proceeds  to  locate  or  stake  it  out  by  measuring 
off  a  parallelogram  1,500  by  600  feet.  Atthe  corners  of  this, 
he  places  piles  of  stones,  and  in  one  or  more  of  them  places 
a  stake  of  ood  on  which  he  writes  his  name,  a  description 
of  his  claim  and  the  date.  At  the  nearest  recorder's  office 
he  files  a  cop^'  of  this  document.  He  must  do  a  certain 
amount  of  improvement  work  on  this  annually,  such  as 
digging  a  ten  foot  hole  or  putting  up  a  cabin  or  some  work 
equivalent  to  the  value  of  $100,  so  as  to  hold  it.  He  may 
also  claim  a  mill  site  on  non-mineral  land  adjacent  not  ex- 
ceeding 5  acres.  Now  the  property  is  his  to  do  as  he  likes 
with  it. 


15 


THE  GEOLOGICAL  TRAINING  OF  A   PROSIECTOR. 

One  of  the  first  things  for  a  prosnector  for  gold  and  silv^er 
to  acquaint  himself  with,  is  the  elements  of  geology.  He 
can  read  this  up  theoretically  in  many  excellent  treatises, 
and  manuals,  such  as  LeConte,  Dana,  and  Shalers'  Manuals, 
and  Geikies'  Hand-Book  of  Field  Geology,  etc.,  and  become 
learned  in  the  names  of  eras  and  epochs,  and  the  jargon  of 
scientific  names  of  fossils  and  minerals,  and  varieties  of 
rocks ;  but  let  him  not  imagine  at  the  end  of  thi*-  process, 
that  he  "  ^^no^as  geology." 

Geology  can  no  more  be  learned  by  means  of  a  book„ 
without  field  work  and  the  actual  personal  contact  with 
nature  and  rocks,  than  chemistry  or  assaying  can  be 
acquired  without  ever  using  a  test  tube  or  a  cupel.  The 
student  maj',  perhaps,  be  unfavorabh^  situated  for  this 
practical  field  work.  There  may  be  no  mountains  or 
upheavals  of  strata,  or  deep  natural  ravines  within  available 
distance  to  study.  He  is  located,  perhaps,  on  the  great, 
monotonous,  flat  prairie.  Very  w^'\\,  then  let  him  study 
what  lies  nearest  him.  This  same  flat,  monotonous  prairie 
has  an  interesting  and  wonderful  history  Let  him  read  up 
what  he  can  find  about  this  in  his  books,  then  go  out  and 
examine  what  he  can  of  the  few  feet  of  horizontal  strata 
exposed  in  some  shallow  water-course  or  dry  ravine; 
examine  minutely,  both  with  eyes  and  microscope,  the 
minerals  composing  these  strata.  Let  him  classify  and 
collect  and  note  the  different  kinds  of  pebbles  scattered 
over  the  surface,  or  in  the  bed  of  a  brook.  Let  him  specu- 
late as  to  the  cause  of  the  undulations  of  the  surface,  the 
deposition  and  peculiar  character  of  the  clays  forming  the 
soil.  Let  him  study  thoroughly  the  geology  of  his  native 
village,  his  immediate  surroundings,  _^rs/.  The  knowledge 
and  practical  habit  of  observation  so  acquired,  will  lead 
later  to  more  extensive  studies  in  wider  fields.  A  student 
may  be  shut  up  in  a  big  city;  let  him  study  the  paving 
stones  of  the  streets  and  visit  the  stone  yards  of  the 
masons.  It  will  pay  him  better  to  take  a  trip  to  some 
dist.int  mountain  region,  than  to  buy  another  expensive 
book  on  geology  after  he  has  mastered  the  first  bare  ele- 
ments. Nothing  like  field  work,  eye  practice,  and  hammer 
practice.  The  student  should  endeavor,  whenever  he 
possibly  can,  to  verify  by  actual  vision  and  personal  experi- 
ence whatever  he  reads  in  his  books.  When  traveling,  let 
him  always  carry  a  geological  hammer  with  him,  and  at  any 


jj^jJ^J^^^^^^^^^^^^i^^^L 


x6 


Sa 


N0,t, 


OOScp 


^fiBLts 


^»NOs 


''"'"''Oqai, 


Oh/\b 


Gyp 


f^eo 


CO/V: 


©t 


O'^C/?/ 


TES. 


^/IR 


Recent  Ano 

«-^ 1, 

MonumentOkoup  o 
N 

T£RT/RRV        5 
Denver  GROUP     J* 

/?fl/\pflHOE  Group 


Laramic  6noup 


oRCTRCeOUS 

MONT/KNA&ROUP 

Q 

Colorado  Group   <* 

O 

Dakota  Group  N 
O 

Id 


Jurassic 


Triassic 


CnRaoNiFCROus 


Silurian 
Cambrian 


Plate  I. 

A  Vertical  Section  of  the  Earth's  Crust  in  Colorado. 


«7 


^ 


station  the  train  may  stop  for  a  few  moments,  step  out  ant^ 
try  to  get  a  specimen  of  the  country  rock  ;  at  the  same  time 
let  him  study  all  he  can  of  the  geology  of  the  country  he 
is  passing  through  from  the  windows  of  the  train,  aided 
perhaps  by  a  geological  map.  The  genuine  prospector  is 
always  looking  about  him,  is  everlastingly  cracking  stones, 
has  always  his  eye  wide  open  for  "  something  kind  o' 
curious." 

If  he  is  near  some  mountain  region,  where,  as  in  Colorado, 
the  whole  strata  of  the  earth's  crust  is  upheaved  and 
exposed,  along  the  mountain  flanks,  in  the  depths  of  the 
canyons,  or  on  the  summits  of  the  peaks,  after  studying  his 
manual,   let  the   student  get,   if  he   can,   some    published 

feological  report  on  such  a  country,  such  as  those  of  the 
J.  S.  Geological  Survey,  abounding  in  illustrations  and 
geological  sections.  Let  him  take  this  book  in  hand  and  go 
to  the  very  place  described  and  pictured  as  a  geological 
section,  and  with  his  hammer  study  each  member  of  the 
section  closely.  This  will  make  him  familiar  with  the 
different  geological  periods,  formations,  rocks,  minerals  and 
fossils,  as  they  actually  appear  in  nature  rather  than  as  his 
i).:agination  has  supposed  them  to  be  from  his  study  of  the 
text  books :  book  geology  and  field  geology  are  not  always 
in  perfect  harmony. 

Having  studied  and  learned  one  local  section  well,  such 
as  that  cut  by  a  stream  along  the  foothills  of  a  mountain 
range,  let  him  repeat  the  course  at  the  other  and  more 
distant  points.  He  will  find  at  each  locality,  though  the 
main  features  are  the  same,  there  is  always  an  interesting 
variety,  such  as  new  fossils,  peculiar  minerals,  changes  of 
dip,  faults,  or  other  structural  peculiarities. 

Along  the  flanks  oi  a  mountain  range,  a  prospective 
prospector  cannot  study  too  many  of  these  geological 
sections.  Having  become  familiar  with  these  foothill  sec- 
tions, he  is  prepared  to  plunge  into  the  heart  of  the  range 
itself.  At  first,  and  for  long  distances  perhaps,  he  will 
encounter  only  granitic  rocks  forming  the  axis  and  core  of 
the  range.  These  are  well  worthy  of  study  and  full  of 
variety.  Later  the  canyon  may  open  into  some  mountain 
valley  or  park,  where  the  strata  he  studied  on  the  foothills 
or  prairie  border  are  again  repeated  and  he  finds  himself 
again  at  home.  Seizing  upon  some  well  defined  and 
familiar  representative  of  a  geological  horizon,  from  this  as 
a  standpoint,  he  soon  reads  off  the  succession  of  the  rest. 
Here,  however,  the  appearance  and  texture  of  the  rocks 


^  t^uE^S^ace^.^T^^. 


i8 


:tlP 


will  probably  be  ditTorent  to  what  they  were  in  the  foothills. 
Heat  has  so  chanjifed  or  metamorphosed  the  sandstones  and 
shales,  that  they  are  scarcely  recofi^nizable  as  the  same  rocks 
as  those  of  the  foothills.  Vet  even  here  a  highly  silicilied 
fossil  shell,  or  a  leaf  impression  on  shales,  or  sandstones 
changed  into  slates  or  quartzite,  will  give  the  prospector 
his  clue  and  his  desired  and  definite  geological  horizon,  and 
he  will  have  little  difficulty  in  again  arranging  and  grouping 
correctly  the  rocky  series'  liut  a  prospector  has  a  "practi- 
cal end"  in  view.  He  is  "after  the  precious  metal,"  gold 
and  silver,  not  after  "pure  science"  or  "fossils  or  sich  '; 
what  practical  use  in  there,  he  may  ask,  in  this  same  careful 
study  of  geological  sections,  where  probably  there  is  not  a 
speck  of  gold  or  silver.'^  Simply  that  minerals  and  metals 
of  economic  value,  such  as  gold  and  silver  are  more  fre- 
quently found  in  the  rocks  of  certain  geological  periods 
than  in  others.  Locally  this  is  especially  true.  For  in- 
stance, nearly  all  the  silver-lead  deposits  of  Colorado  are 
found  in  a  certain  bed  of  limestone  not  over  200  feet  thick, 
to  be  found  only  in  one  geological  period  out  of  many 
others,  viz.:  the  lower  division  of  the  Carboniferous.  It 
would  naturall}"^  then  be  advisable  for  a  Colorado  prospector 
to  be  able  surely  to  identify  this  limestone,  as  well  as  the 
geological  horizon  in  which  it  occurs,  among  the  various 
other  limestones  of  various  other  periods  and  ages  in  the 
mountains. 

Again,  gold  is  mainly  confined  to  crystalline  rocks  of 
Archx'an  age  or  to  porphyries  associated  with  these.  A 
prospector  should  be  familiar  with  these  rocks  and  their 
varieties.  Gold  is  also  found  in  the  placers  derived  largely 
from  the  breaking  up  of  these  rocks;  the  ability  to  distin- 
guish the  diflferent  pebbles  may  lead  to  the  source  whence 
the  gold  was  derived.  Familiarity  with  rocks  of  all  kinds  is 
a  necessary  prospector's  education  in  itself. 


GEOLOGICAL   SECTIONS   OF   COLORADO. 

In  illustration  of  what  we  have  said,  let  us  take  the  two 
engraved  generalized  sections  showing  all  we  know  of  the 
crust  of  the  earth  as  exposed  in  Colorado.     Plates  I  and  II. 

Plate  I  is  a  vertical  section  of  an  ideal  cliff,  showing  all 
the  members  of  the  various  periods  in  a  stupendous  cliff 
resting  on  fundamental  Archoean  granite  at  the  bottom  of  a 
canyon.  Plate  II  represents  the  same  rocks  and  succession 
of  strata  displayed   in   upturned  "hog   backs"  along   the 


19 


flanks   of  the    mountains  and  foothills   on   the   border  of 
mountain   and    prairie.     Roth   of   these   -^  ^^,'^^ 
"generalized-    or   "  made    up  '   of    actmil    P^/t.al    tyi  ca 
sections  found  in  different  localities  in  Colorado.^the  vertical 


av>l»l«\^*A     x^ifciic 


can  be  seen  by  the  traveler  from  the  windows  as  he  glides 
throueh  in  the  railway  car,  and  the  inquiring  prospector  or 
geologist  can  examine  and  study  this  vast  section  leisurely 
on  his  mule  or  on  foot,  without  doing  any  climbing  and  on 
a  good  road.  Smaller  partial  sections  can  be  similarly 
studied  along  many  of  the  streams  issuing  from  the  Kocky 
Mountains    among   the   foothills   of   Colorado,     buch,   tor 


19 


flanks  of  the 
niouiitain  and 
"fi^cncralized 


inoutitains  and  fcjothills  on 
prairie.  Both  of  these  are 
or    "made    up'    of    actual 


the  border  of 
ideal  sections 
partial    typical 


sections  found  in  dilTerent  localities  in  Colorado,  the  vertical 


Grani/-e  4  Gfte/Si  tviHf  Porphyry 
Gold.  j//yer  Lead,  I  tort 


ARCH/tAN 


V 


\     Do/o.mife 
'  *  fiorpkyrv 


('onglomerate 

TRIASSIC 


I' 


# 


Iron 


t 


A/lounta/zi 


^  and 


Path    Region 


I 

^ 


^  ^ 


Footh'ilh 


Pr,ATE   II. 
Generalized  Section  of  Rocky  Mountains  in  Colorado,    Showing  Economii 


can  be  seen  b)'  the  traveler  from  the  windows  as  he  glides 
through  in  the  railway  car,  and  the  inquiring  prospector  or 
geologist  can  examine  and  study  this  vast  section  leisurely 
on  his  mule  or  on  foot,  without  doing  any  climbing  and  on 
a  good  road.  Smaller  partial  sections  can  be  similarly 
studied  along  many  of  the  streams  issuing  from  the  Rocky 
Mountains    among   the   foothills    of  Colorado.     Such,    for 


/.aya 


MaP/affM 


/^  £kr  A  i:  E 


'a  ir  $ 


L6v^erjjp%f  ll'viSAfV  Colly/do  ''(iroup^^r:"''^rLat^^M^:^^xitoup 


TERTIARY 


At/ej/ci.1  Baiiftss:  /'.^f/oty ^ooft  f 


>4 


I 


btoup 


Footti'ilh     and    Hogbdclf^ 


' V 

Plate  II. 

s  in  Colorado,    StiowiiiR  Economical  Products  in  Different  <ieological  Horizons  and  Strata, 


->  V 


Table    Land3 

V" 


--/v. 


Plains 
>• — 


\ 


9 


t8 


will  probably  be  ditfcrent  to  what  tbey  wore  in  the  loothills. 
Heat  has  so'chan>,a'fi  or  metaiiiorphosed  tlie  sandstones  and 
shales,  that  they  are  scarcely  rei-ojrnizai)le  as  the  same  rocks 

•«  f    ■»  '     .*I.MI«         Vr,*    niFon    Vtorp  -I    liiirlilv   SMIClllcd 


I 


I 
I 


In  illustration  of  what  we  have  said,  let  us  take  the  two 
engraved  generalized  sections  showing  all  we  know  of  the 
crust  of  the  earth  as  exposed  in  Colorado.     JMates  I  and  II. 

Plate  I  is  a  vertical  section  of  an  ideal  cliff,  showing  all 
the  members  of  the  various  periods  in  a  stupendous  cliff 
resting  on  fundamental  Archx*an  granite  at  the  bottom  of  a 
canyon.  Plate  II  represents  the  same  rocks  and  succession 
of  strata  displayed   in   upturned  "hog  backs"  along  the 


19 


Hanks  ot  the  mountains  and  foothills  f)ij  the  borrlcr  of 
mountain  aiul  prairio.  Roth  of  these  are  ideal  sections 
" j^enerali/efi  "  or  "made  up"  of  actual  partial  typical 
sections  found  in  dilTerent  localities  in  Colorado,  the  vertical 
one  in  detachefl  and  sometimes  wiflely  separated  districts  in 
the  heart  of  the  nujuntains;  the  other  at  similarly  distinct 
and  different  localities  alonjj^  the  l)anks  of  the  various  rivers 
issuinjj^  from  these  canycjns  in  the  mountains,  cuttinj^  their 
way  throujj[h  the  upturned  strata  of  the  llankinjj;  foothills 
and  debouchinj^  on  the  prairie. 

It  is  very  rare  to  find  at  one  locility  anywhere  in  the 
world,  a  complete  section  of  the  earth's  crust  exposed.  The 
nearest  approach  io  this  in  Colorado,  is  the  remarkatile 
section  between  Coh^rado  Springs  and  Manitou,  which 
shows  alonj^  the  waj^on  road  the  successi(jn  of  strata  from 
Arcluian  to  (Juaternary. 

One  of  the  most  remarkable  vertical  sections  in  the 
W(jrld,  is  in  the  grand  canyon  (jf  the  Colorado  Ri\er,  where 
the  stupendous  clifTs  show  in  one  face,  a  thickness  of  some 
6,000  to  7,000  feet  of  strata,  representing  several  geological 

Ceriods,  but  by  no  means  a  complete  section  of  all  that  is 
ncnvn  of  the  earth's  crust. 

To  show  how  ditFicuit  and  rare  it  is  to  to  get  a  complete 
secticjii  of  ^;// the  periods  in  the  earth's  crust,  we  may  state 
that  sometimes  the  rocks  of  a  single  geological  period  are 
from  10,000  to  20,000  feet  thick.  A  canyon  might  thus  be 
cut  to  a  depth  of  5.000  feet,  and  yet  be  in  only  part  of  a  single 
earth-period. 

By  lar  the  most  extensive  and  available  sections  are,  like 
those  represented  in  the  engraving,  along  the  courses  of 
streams  on  the  Hanks  of  a  mountain  range.  It  would  be  a 
formidable  task  to  scale  a  cliff  5,000  feet  high  and  examine 
minutely,  in  ascending,  each  of  its  geological  divisions; 
whilst,  on  the  other  hand  in  the  foothill  regions,  a  pros- 
pector may  walk  over  and  mark  and  study  as  nmch  as  10,000 
to  40,000  feet  of  strata  along  the  banks  of  a  river  in  a  single 
aftcnoon.  In  the  Weber  Canyon  in  Utah,  as  much  as  40,000 
feet  of  strata,  composing  the  flanks  of  the  Wahsatch  Range, 
can  be  seen  by  the  traveler  from  the  windows  as  he  glides 
through  in  the  railway  car,  and  the  inquiring  prospector  or 
geologist  can  examine  and  study  this  \'ast  section  leisurely 
on  his  mule  or  on  foot,  without  doing  any  climbing  and  on 
a  good  road.  Smaller  partial  sections  can  be  similarly 
studied  along  many  of  the  streams  issuing  from  the  Rocky 
Mountains    among   the    foothills    of  Colorado.     Such,    for 


20 


I 


II 


example,  as  at  Boulder  Creek,  Clear  Creek,  Bear  Creek,  the 
Platte  River,  and,  most  complete  of  all,  the  one  along 
Fountain  Creek,  near  Colorado  Spiings,  which  we  have 
already  mentioned.  Similar  sections  can  be  found  in  most 
mountain  regions,  such  as  the  Adirondacks  in  the  East,  and 
the  Sierra  Nevada  and  Coast  Range  in  the  West  of  America. 
We  emphasize  again,  that  the  close  study  of  these  is  the 
best  preliminary  step  we  know  of  in  a  j^  rospector's  geological 
education.  Let  us  now  examine  our  ideal  generalized 
Colorado  section  which  we  will  suppose  to  be  all  exposed 
along  the  banks  or  canyon  of  a  single  river.  We  will  start 
from  the  Archaean  granite  in  the  canyon,  thus  giving  us  a 
sure  and  known  and  lowest  possible  geological  horizon  to 
begin  with. 

THE   ARCH.1i AN. 

This  Archaean  we  find  to  be  composed  towards  its  core, 
of  solid,  shapeless  (amorphous)  crystalline  granite,  which 
seems  to  have  been  fused  out  of  all  shape  by  water  and  lire, 
or  aqueo-igneous  fusion.  With  this,  but  more  characteristic 
of  the  upper  and  outer  edge  of  the  Archaean,  the  granite 
assumes  a  more  stratified  and  bedded  character,  which  we 
designate  as  "gneiss  "  and  interbedded  with  it  at  intervals 
are  distinctly  laminated  or  finely  leafed  strata,  called  schist; 
all  these  varieties  are  composed  of  the  same  minerals  in 
different  arrangement  and  quantity,  viz.,  mica,  quartz,  horn- 
blende, and  feldspar.  As  these  rocks  are  semi-igneous  or 
metamorphic,  we  find  no  fossils  in  them.  Traversing  all 
these  Archa;an  rocks  and  cutting  them  at  all  sorts  of 
angles,  we  may  notice  some  eruptive  dykes  of  porphj-rv, 
which  were  once  certainly  molten  and  have  ascer.ded  in 
that  state  through  fissures  opened  in  the  rocks  from  depths 
and  sources  unknown.  As  we  approach  the  edge  of  the 
granite  we  may  even  see  some  of  these  molten  rocks, 
insinuating  once  fiery  tongues  among  the  weak  places  and 
bedding  planes  of  the  overlying  sedimentary  strata,  as 
represented  in  the  diagram,  where  one  dyke  is  shown  to 
have  sent  out  so  thick  an  intrusive  sheet  of  porphyry, 
(see  Plate  II),  between  the  overlying  limestones,  that  where 
subsequent  erosion  took  place,  this  thick  sheet,  by  its 
superior  hardness,  was  left  to  form  the  highest  cap  of  the 
mountain,  as  on  many  of  our  prominent  mountain  peaks 
such  as  Mt.  Lincoln  and  others  in  South  Park. 

Besides  these  rocks,  the  prospector  will  observe  numbers 
of  quartz  and  pink  feldspar  veins  of  all  sizes,  some  mere 


21 


streaks  and  occupying  incipient  fissures  or  weak  places 
(veins  of  segregation),  others  occupying  large  well  defined 
fissures  or  jointing  planes  (so  called  true  fissure  veins). 
Some  of  these  may  or  may  not  carry  metal,  gold  or  silver, 
lead  or  copper,  at  any  rate  he  will  pay  them  especial  atten- 
tion particularly  if  any  of  them  look' at  all  decomposed  or 
rusty,  or  are  in  close  proximity  to  an  eruptive  porphyry 
dyke. 

THE  CAMBRIAN. 

Now  the  prospector  emerges  from  the  Archiean  granite 
and  finds  the  first  true  sedimentary,  water-formed  rocks 
lying  where  the  ancient  seas  placed  them,  on  the  eroded 
upturned  edges  of  the  granitic  series. 

If  this  section  should  be  near  the  plains  or  foothills, 
this  first  sedimentary  rock  will  be  a  sandstone,  pure  and 
simple,  or  a  conglomerate  of  little  pebbles,  but  in  the  parks 
and  center  of  the  mountains  where  these  ancient  strata  are 
most  conspicuous,  the  first  rock  lying  on  the  granite  is  a 
hard,  white,  semi-crystalline  quartzite  or  metamorphosed 
sandstone.  He  may  possibly  find  some  obscure  signs  of 
ancient  fossil  shells  in  this  series,  which  is  called  the  Cam- 
brian now,  though  formerly  it  was  held  to  be  only  a  lowei 
division  of  the  Silurian.  In  Colorado  these  Cambrian  rocks 
rarely  exceed  200  or  300  feet  in  thickness,  but  in  other 
regions  they  are  often  very  much  thicker.  In  this  series 
the  prospector  may  look  for  precious  ore,  more  especially 
gold.  He  will  carefully  look  also  for  intrusions  of  eruptive 
porphyry  in  this  series,  as  at  the  junction  of  this  with  the 
quartzite,  ore  is  most  likely  to  be  found.  He  will  also 
observe  any  rusty  signs  filling  cracks,  as  good  indications 
of  gold  bearing  ore.  Silver  also  may  be  found  associated 
with  lead  or  zinc. 

SILURIAN. 

Walking  along,  he  next  comes  to  some  200  or  300  feet  of 
drab-yellowish  or  light  gray  thin  bedded  limestone  of  a 
dolomitic  character,  characterized  by  numbers  of  little  white 
flints  or  (rarely  in  Colorado)  by  some  fossil  shells,  which,  by 
reference  to  the  engravings  in  his  manual,  he  finds  to  be 
Silurian,  and  so  recognizes  the  series.  Here  he  may  find 
indications  of  lead,  silver  or  other  ores,  but  not  much  gold 
as  a  rule. 

CARBONIFEROU.S. 

The  next  series  of  this  should,  according  to  the  text- 
books, be  the  Devonian,  characterized  by  fossil  fishes  and 


22 


I 


*'()ld  Red"  sandstones;  but  tht  rocks  of  this  epoch  for 
some  reason  are  missing  in  C  )iorado.  Instead  of  this,  rest- 
ing on  the  Silurian,  he  finds  a  thick  bed  of  heavy  bedded, 
massive, "  blue-grey  "  limestone,  characterized  by  black  flints, 
and  at  rare  intervals  by  fossil  shells  and  corals,  which  again, 
by  reference  to  his  book,  he  finds  to  be  characteristic  of  the 
Lower  Carboniferous.  This  limestone  when  traversed  by 
sheets  of  eruptive  porphyry,  has  yielded  at  Leadville  and  at 
Aspen  and  New  ^Iexico  and  Arizona,  some  of  the  largest 
si'/er-lead  dep<;sits  in  the  West.  In  fact,  throughout  the 
West  it  may  be  considered  as  the  main  silver-lead  horizon. 
This  limestone  is  generally  betv/een  200  and  300  feet  in 
thickness  and  readily  recognized  by  its  position  relativ'e  to 
the  Silurian  below  it.  and  the  massiveness  of  the  strata,  and 
their  dark  grey  color.  It  is  commonly  called  the  "  Blue 
Limestone  "  in  Colorado. 


I  ^ 


MIDDLE   CARBONIFEROUS. 

Next  on  this,  is  a  bed  of  dark  black  shales  in  which  thin 
seams  are  sometimes  found,  and  fossil  plants,  like  those  in 
the  coal  strata  of  Peunsylvania,  sufficient  to  show  that  it. 
too,  belongs  to  the  Carboniferous.  This  is  followed  by 
some  2,000  or  more  feet  of  "grits,"  rough,  hard,  gritty 
sandstones,  partially  changing  into  quartzite,  akin  to  the 
••  mill-stone  grits"  of  the  Eastern  States.  A  few  limestones 
occur  in  this  thick  Middle  Carboniferous  series,  which 
locally,  when  capped  by  porphyry,  produce  silver-lead 
deposits  ;  but  generally  speaking,  the  "grits  "  are  unproduc- 
tive in  Colorado. 

The  Upper  Carboniferous  consists  of  beds  of  gypsiferous 
shale  and  heavy,  brownish  red  conglomerate  sandstones. 

TRIASSIC  "RED-BEDS," 

From  these  we  pass  into  a  series  of  heavy  bedded,  coarse 
conglomerate  sandstones  of  a  brick-red  color,  commonly 
known  as  the  "  Red  Bed?  "  in  Colorado  ;  little  indications  of 
ore  are  to  be  expected  in  this  series.  The  prevailing  redness 
of  the  series  makes  it  an  easUy  recognized  geological  horizon 
in  Colorado  and  elsewhere.  The  thickness  in  Colorado 
varies  from  1,000  to  2,000  feet. 

JURASSIC. 

Next,  the  prospector  comes  to  a  softer  and  more  varie- 
gated   series,   consisting    largely    of    pink,  green,    red,   or 


23 

maroon  marls  and  clays,  with  some  thin  limestones  and  red 
sandstones.  This  is  the  Jurassic  series  in  which  some 
remarkable  lizard  remains,  called  Dinosaurs,  have  been 
found,  proving  the  correctness  of  its  Jurassic  name.  This 
is  not  a  likely  mineral  horizon,  generally  speaking,  in 
Colorado. 

CRETACF.OUS. 

These  softer  beds  are  capped  by  a  hard  massive  sandstone 
about  200  feet  thick,  forming  by  reason  of  its  superi(jr 
hardness  a  prominent  hog  back  in  the  prairie  or  foothill 
region.  Fossil  remains  of  leaves  show  it  to  be  a  land  and 
fresh-water  group,  which  is  called  the  Dak   '  di  group. 

This  group  in  Colorado  forms  the  base  of  the  great 
Cretaceous  system  ;  lying  on  it,  is  an  enormous  thickness 
(jf  drab  shales  with  a  few  limestones  characterized  by  fossil 
sea  shells,  showing  the  group  to  be  the  marine  Cretaceous, 
likewise  a  poor  prospecting  ground.  Towards  the  upper 
portion,  these  shales  pass  gradually  into  heavy  bedded 
sandstones  containing  several  seams  of  coal,  and  many 
impressions  of  tropical  foliage.  This  is  the  Laramie  group 
of  the  Cretaceous,  evidentl}'^  of  fresh  water  origin,  and 
noted  as  the  main  coal  producing  horizon  in  Colorado  and 
the  West. 

TERTIARY. 

On  this,  at  a  somewhat  gentler  angle  even  to  horizontality, 
rest  thick  beds  of  shale  and  claj'^  and  conglomerate,  com- 
posed of  volcanic  detritus  and  pebbles,  showing  that  at  the 
time  these  Tertiary  beds  were  being  laid  down  by  large 
fresh  water  lakes  and  marshes  surrounded  by  tropical 
foliage,  volcanic  eruptions  on  a  grand  scale  repeatedly 
occurred.  Hence  it  is  that  many  of  the  Tertiary  beds  are 
preserved  from  erosion  by  being  capped  with  v^jlcanic 
rocks,  such  as  basalt,  andesite,  or  rhyolite,  as  at  the  Table 
Mountains  at  Golden,  on  the  Divide  near  Colorado  Springs, 
and  elsewhere  in  Colorado.  One  of  these  lava  capped 
"mesas"  is  represented  in  the  section,  Plate  II.  Fossil 
leaves  and  coal  seams  are  found  in  this  period. 

QUATERNARY. 

Lastly,  strewn  indiscriminately  over  all  the  formations  is 
the  "  Ouaternary  drift "  composed  of  loose  pebbles,  and 
sands,  and  clays,  the  material  derived  from  rocks  of  all  the 
periods  through  the  agency  of  glaciers  and  streams. 


Here  the  prospector  will  pan  for  his  ^old  placer,  and  in 
his  search  may  possibly  come  across  the  teeth  or  tusks  of 
the  great  Mammoth  or  fossil  elephant,  together  with  the 
first  indications  of  the  presence  of  primitive  man.  The 
pebbles  by  their  variety  will  form  a  fertile  subject  of  study 
to  determine  to  what  class  of  rocks  they  belong. 

This  ends  the  prospector's  first  preliminary  lesson  in 
Colorado;  but  taking  this  section  as  a  type,  he  may  to  his 
great  advantage,  similarly  study  other  sections  far  remote 
from  Colorado. 

In  Colorado,  if  he  knows  this  section  by  heart,  he  has 
the  key  to  nearly  all  our  mountain  structure,  and  will  be  at 
home  wherever  he  goes.  He  will  be  struck,  too,  to  see  to 
how  small  a  portion  of  this  great  section  the  precious 
metals  are  more  or  less  confined,  principally  to  the  Archai^an 
and  Paleozoic  rocks. 


CHAPTER  II. 


'I 


THE    PROSPECTOR'S   HISTORICAL    GEOLOGY. 

In  our  last  chapter  ,ve  gave  some  hints  to  the  prospector 
how  to  commence  his  geological  studies,  and  gave  him  an 
example  of  a  geological  section  o<"  the  foothills  and  moun- 
tains of  Colorado,  and  how  to  otudy  it  in  detail  practically. 
Having  completed  this  study,  if  a  thoughtful  man,  he  will 
like  to  know  more  of  the  natural  history  of  all  this  section  of 
the  earth's  crust :  what  is  the  natural  history  of  the  Archa,'an, 
the  Cambrian,  Silurian,  etc.,  why  do  some  of  these  strata 
contain  sea  shells,  ?.nd  others  land  plants,  why  are  some 
evidently  of  marine,  and  others  of  fresh  water  origin,  and 
particularly  why  are  some  especially  metalliferous,  and 
others  not  so  much  so.  We  propose,  therefore,  in  this 
chapter  to  give  him  a  brief  sketch  of  the  earth's  history  as 
exemplified  in  the  section,  Plates  I.  and  II. 


HYPOTHETICAL  ORIGIN  OB'  THE  EARTH. 

The  world  was  not  "  spoken  into  existence  ready  made  " 
in  the  state  we  now  find  it.  It  has  attained  this  condition 
through  a  multitude  of  gra  -al  changes  and  revolutions 
which  have  taken   millions      '    rears  to  accomplish.    The 


I 


25 


'i 


remote  history  of  the  earth's  origin  is  a  matter  of  hypothesis 
and  speculation.  There  arc  reasons  for  supposing  that  at 
(jne  time  its  elements  were  in  a  gaseous  condition,  and  that 
this  planet  was  an  incandescent  luminous  cloud  revolving 
through  space,  gradually  consolidating  into  a  molten  ball 
surrounded  still  by  an  atmosphere  of  gases,  a  condition 
perhaps  not  very  unlike  that  of  the  sun,  whose  interior  by 
some  is  supposed  to  be  passing  into  the  molten  state,  while 
its  exterior  consists  of  various  incandescent  gases  arranged 
more  or  less  according  to  their  specific  gravities.  The 
spectroscope  has  detected  the  elements  of  some  of  our  earth 
metals  and  minerals  in  the  sun  in  >  tate  of  vapor.  The 
ultimate  source  of  the  precious  mei...s  is  again  a  matter  of 
speculation  like  the  nebular  hypothesis  we  have  alluded  to, 
by  which  the  earth,  as  we  have  said,  is  supposed  to  have 
arrived  at  its  present  condition  as  the  result  from  the 
gradual  cooling  of  an  incandescent  mass,  and  as  the  specific 
gravity  of  the  crust  is  much  lesf.  than  that  of  the  whole 
mass  of  the  earth,  it  has  been  i.iferied  that  the  heavy  metals 
must  be  in  much  larger  proportion  in  the  interior  of  the 
earth,  than  in  the  rocky  crust,  though  this  greater  interior 
specific  gravity  might  be  also  accounted  for  by  the  rocks  of 
trie  interior  being  much  more  tightly  packed  by  enormous 
pressure  than  those  near  the  surface.  Volcanic  emanations 
and  hot  springs  contain  metallic  minerals,  so  also  do  the 
waters  of  the  ocean.  But  we  know  not  from  what  depth  the 
former  came,  nor  from  what  source  the  latter  dcved  them. 
As  circulating  waters  take  up  and  throw  down  their  metallic 
contents  under  varying  conditions,  the  same  material  may 
have  been  deposited  more  than  once,  and  in  more  than  one 
form  since  it  reached  the  rocky  crust. 

l^pon  the  cooling  of  the  ball,  a  crust  formed  like  that  on 
molten  iron,  crumpled  and  corrugated  by  contraction,  due  to 
cooling,  into  an  uneven  surface,  with  comparatively  slight 
elevations  and  depressions,  and  doubtless  broken  through 
here  and  there  by  great  fissures  and  volcanic  craters,  through 
which  the  molten  flood  beneath  poured  out  in  volumes, 
adding  to  the  thickness  of  the  congealing  crust. 

Upon  such  a  surface  the  gaseous  atmosphere,  gradually 
cooling  and  condensing,  descended  as  hot  chemical  rain,, 
and  filled  the  troughs  of  the  crumpled  surface  with  a  hot, 
chemical,  steamy  ocean.  Whatever  land  of  primitive  lava 
rose  above  this  ocean  was  battered  by  the  waves,  reduced 
to  sediment,  and  deposited  as  the  first'sedimentary  strata  in 
the  bed  of  that  prima3val  ocean,  the  eruptions  from  below 


!■ 


.    I 


h  i 


r  ! 


26 

the  thin  crust  doubtless  contributing  largely  to  the  same 
material. 

ARCH.EAN   AGE. 

Thus,  perhaps,  were  formed  the  first  stratified  rocks  of  the 
world,  which  we  have  an  opportunity  of  actually  seeing  and 
studying,  viz.:  the  granitic  series,  with  its  varieties  of  gneiss, 
schist,  syenite,  etc.,  and  as  this  is  the  beginning  age  so  far 
as  we  know,  we  call  it  the  Archaean,  the  Greek  for  begin- 
ning. It  would  seem  probable,  however,  that  these  granitic 
rocks  forming  the  axes  of  our  mountains,  may  not,  at  least 
in  part,  have  been  the  very  first  rocks  of  the  crust,  for  we 
observe  some  of  them  such  as  the  gneisses  and  schists  to  be 
stratified,  and  to  show  elements  in  them  seemingly  derived 
from  other  and  still  older  rocks,  which  latter  may  or  may 
not  have  belonged  to  the  original  cooling  crust.  Some 
geologists  claim  that  the  Archajan  is  the  first  cooled  crust 
and  attribute  it  to  a  molten  origin.  This  may  be  true  for 
the  seemingly  fused  massive  amorphous  granites  (though 
these  may  be  but  the  result  of  aqueo-igneous  fusion  of 
sediment  or  extreme  metamorphic  action),  but  scared}'  for 
the  stratified  gneisses  and  schists,  though  it  is  to  be  noted 
that  a  sort  of  stratified  or  schistose  structure  is  sometimes 
observed  in  truly  igneous  rocks  and  may  be  induced  by 
peculiar  arrangement  of  minerals,  pressure  and  cleavage, 
instead  of  water  lamination. 

The  subject  is  a  difficult  one  and  too  abstruse  for  the 
limits  of  this  work. 

In  the  scale  of  geological  periods  in  the  text-books,  we 
sometim  es  find  this  great  Archaean  divided  into  two  or 
more  groups  such  as  the  Laurentian,  Huronian  and  of  late 
the  Algonkian.  The  Laurentian  is  the  oldest  and  may  be 
called  the  Archaean  proper,  wliilst  Huronian  and  Algonkian 
may  be  grouped  generally  as  Pre-Cambrian,  or  series  of 
rocks  laid  down  after  the  Laurentian  and  before  the  Cam- 
brian. All  the  rocks  are  of  a  highly  crystalline  order  and 
bave  a  peculiar  and  distinct  general  appearance  different,  as 
a  rule,  to  those  of  any  subsequent  geological  periods  and  so 
not  easily  mistaken  for  them,  consisting  in  the  lower  division, 
mainly  of  granite,  gneiss  and  schists,  and  in  the  upper 
divisions  of  gneisses,  schists,  quartzites,  slates,  some  marble, 
serpentine,  etc.  The  upper  or  Pre-Cambrian  series  is  not 
nearly  so  universally  found  as  the  Laurentian  or  Archaean 
proper.  In  Colorado  we  find  the  Pre-Cambrian  represented 
locally  in  South    Boulder  and  Coal  Creek  canyons,  along 


n 

the  foothills,  also  near  Salida  in  the  Arkansas  valley,  in  the 
Ouartzite  range  and  on  the  road  between  Ironton  and 
Ouray  in  the  San  Juan  Mountains.  The  new  Kootanie 
silver  mining  district  of  British  Columbia,  seems  to  be 
largely  in  these  Pre-Cambrian  rocks.  This  Pre-Cambrian 
is  usually  very  thick,  numbering  many  thousands  of  feet. 

It  is  distinct  from  the  Archaian  prober  or  Laurentian  by 
lying  on  tht  latter  at  a  different  angle,  in  other  words 
•unconformable."  The  rocks,  too,  do  not  contain  so  much 
of  the  heavy  massive  granites,  and  heavy  bedded  gneisses 
as  the  Laurentian,  but  are  more  characterized  by  quartzites, 
by  conglomeratic  gneisses  and  schists,  and  show  clearly 
that   though  highly  metamorphosed  and  crystalline,]?  they 


Plate  III. 

Archaean  Rocks. 

are  of  true  fragmental  and  aqueous  origin,  for  the  pebbles 
in  the  gneiss  are  often  very  distinct,  and  ripple  marks  are 
not  uncommon  on  the  quartzites  and  slates  and  schists. 
The  material  was  doubtless  derived  by  waters  from  that  of 
the  underlying  and  older  Laurentian.  The  whole  Archaean 
series,  however,  has  evidently  passed  through  an  ordeal  of 
heat,  such  as  is  called  aqueo-igneous  heat,  and  all  its  ele- 
ments are  in  a  highly  crystalline  condition.  Its  strata  are 
intensely  folded  and  crumpled.     See  Plate  III. 

Signs  of  life,  in  the  upper  series  even,  are  exceedingly 
obscure  and  doubtful,  such  as  graphite  and  possibly  corals. 
Great  iron  beds  also  occur,  indirect  proofs  perhaps  of  the 
previous  existence  of  life. 


28 


I  I 


•'     i 


li 


We  have  been  thus  particular  with  this  Archxan  Age 
because  its  rocks  are  of  great  importance  to  the  prospector, 
being  the  main  repositories  of  gold,  silver  and  the  precious 
metals  thoughout  the  world.  Moreover  many  of  the  other 
and  newer  rocks  containing  gold  and  silver  have  been  made 
from  the  detritus  of  this,  and  the  gold  placer  beds  largely 
from  the  detrituo  of  the  rocks  and  porphyries  found  in  this 
age.  Thus  the  Archaean  may  be  considered  as  the  parent 
of  nearly  all  the  other  rocks.  When  later  we  have  studied 
the  origin  of  ore  deposits,  we  shall  see  how  eminently  the 
Archxan  Age  with  its  attendant  heat,  chemical  reactions, 
Assuring,  metamorphism  and  volcanic  eruptions  was  favor- 
able to  the  diffusion  and  concentration  of  precious  ores  in 
its  rocks. 

CAMBRIAN  AND  SILURIAN  AGES. 

Cooling  and  consequent  contractions  still  progressing  in 
the  globe,  fresh  and  greater  wrinkles  and  corrugations 
were  caused  on  the  surface  of  its  crust,  and  some  of  these 
granite  seabottom  strata  were  crumpled  up,  till  the 
crumples  arose  above  the  then  universal  ocean  as  low 
islands  or  reefs.  The  ocean  had  by  this  time  cooled 
sufficiently  to  support  low  forms  of  marine  life,  and  so  along 
the  flanks  of  these  granitic  islands,  coraJs  formed  reefs, 
shell  fish  swarmed  and  sea  weeds  grew.  Sands  formed  by 
the  waves  from  the  material  of  the  granite  were  laid  down 
as  shore-line  beaches,  often  mixed  with  shells ;  and  in 
deeper  water,  corals  were   forming   limestones   as   at   the 

E resent  day,  both,  by  time  and  pressure,  consolidating  into 
ard  rock,  eventually  it  may  be,  metamorphosed  by  heat 
into  a  semi-crystalline  hardness,  as  in  the  case  of  the 
Cambrian  quartzite  and  Silurian  limestones,  the  latter  some- 
times changed  to  marble.  If  these  Cambrian  quartzites 
were  formed  from  the  detritus  of  the  granite  and  the 
granitic  series  is  the  source  of  gold,  it  is  not  surprising  that 
we  find  the  Cambrian  quartzites  locally  rich  in  gold,  as  they 
were  the  auriferous  sea  beaches  (like  those  of  to-daj^  in 
California  which  are  gold  bearing)  of  that  period,  later 
consolidated  into  hard  rock.  In  Colorado  the  Cambrian 
quartzites  are  only  locally  prolific  in  gold,  as  at  Red  Cliff, 
but  as  they  have  hitherto  been  much  overlooked  by  pros- 
pectors they  are  worthy  of  closer  attention  by  the  gol.l 
seekers.  The  limestone  not  being  of  a  true  fragmental 
origin  but  formed  by  the  slow  work  of  corals,  could  not  be 
expected   on   consolidation  to  be  a  recipient  of  gold,  but 


39 

later  by  its  peculiar  chemical  C(jinposition,  of  which  we  will 
speak  hereafter,  and  by  its  cavernous  nature,  it  furnished  a 
more  convenient  receptacle  for  silver  and  lead  ores. 

So  then  in  Colorado  and  in  other  regions,  we  find  first 
the  upheaved  crumpled  granite  of  the  old  Archaean  island, 
and  on  these  the  Cambrian  sandstone  or  quart/ite  beach  of 
"golden  sands"  with  some  fossil  shells,  and  upon  this  again 
Silurian  limestone  with  relics  of  fossil  corals  and  shells.  So 
we  call  these  ages  the  Cambrian  and  Silurian  because  the 
fossil  shells  and  corals  are  peculiar  to  those  ages  and  distinct 
from  those  of  later  periods  or  the  present  day. 


Plate  IV. 

America  at  Close  of  Archaean. 

North  America  at  the  beginning  of  these  periods  was 
barely  outlined  by  a  few  granite  islands  congregating  mainly 
in  the  region  now  occupied  by  Canada,  wnilst  one  or  two 
reefs  or  scattered  chains  of  islands  marked  the  site  of  the 
Eastern  ranges  of  mountains,  and  a  few  parallel  granite 
islands  outlined  the  site  of  the  principal  uplifts  or  future 
great  ranges  of  the  Western  Cordilleras.  All  else  was 
ocean,  and  that  ocean  was  depositing  its  Cambrian  beaches 
and  Silurian  coral  limestones  against  or  near  these  granite 
islands  destined  in  time  to  grow  into  lofty  mountain  ranges. 


30 

and  to  bcconif  the  Ijackbone  of  the  American  Continent. 
See  Plate  IV. 

DEVONIAN. 

The  Devonian  which  should  come  next  in  order  in  the 
geological  tree  appears  to  be  absent  in  Colorado  but  is  well 
shown  at  the  Eureka  Mines  in  Nevada.  The  rocks  appear 
to  be  mostly  r.arine  limestone  full  of  corals  and  shells  and  a 
few  remains  <  f  gigantic  fishes  for  which  this  age  was 
celebrated.  Land  plants  and  some  coal  are  found  in  it  in 
the  East.  Lead  silver  ores  may  be  expected  in  the  lime- 
stones of  this  age,  and  in  Cornwall  (England)  Devonian 
slates  traversed  by  quartz  porphyries  are  the  main  rocks 
carrying  tin  ore,  a  metal  very  scarce  at  present  in  North 
America. 


pi^';XS"^'^<7/^. 


S^-^/^. 


Cenozoic 


Plate  V. 

Section  showing  Unconformity  of  Geological  Eras. 

These  ages  we  are  speaking  of  are  separated  or  distin- 
guishable from  one  another  by  decided  and  characteristic 
changes  in  the  fossil,  animal  and  vegetable  life  existing 
between  one  age  and  another,  also  in  some  countries  by 
marked  unconformability  of  the  rocks,  /.  c,  the  rocks  of  one 
age  lying  at  a  different  angle  upor  the  upturned  rocks  of  a 
previous  age  marking  great  oscillations  between  sea  and 
land. 

In  America,  however,  these  oscillations  between  sea  and 
land  seem  to  have  been  less  than  in  Europe,  and  we  find  a 
general  uniform  rise  of  the  continent  from  the  primitive 
oceans,  and  an  orderly  succession  of  strata  lying  against  the 
flanks  of  the  ever  rising  granite  nucleus  of  both  mountains 
and  continent.  Hence  to  distinguish  the  dilTerent  ages  we 
are  driven  more  to  the  study  of  fossils  and  lithological 
peculiarities  than  deriving  anv  help  from  observed  marked 
uncontormabilitv.     See  Plate  V,  in  which  the  strata  of  the 


3» 

flilTcrcnt  cms  lie  upon  one  another  cit  different  anjjfh's.  and 
tiie  glacial  and  (juaternary  drift  pebbles  and  clays  are 
strewn  unconlorniably  also  ovxm'  the  tops  of  ihc  uptilted  and 
er(jdud  strata  of  all  the  eras  beneath. 


CAkHONlKKKOUS. 

In  the  Kastern  States  as  the  American  continent  jj^radnally 
rose  from  the  sea,  and  to  the  granite  islands  had  been  added 
a  Cambrian,  Silurian,  and  Devonian  shore,  with  further 
unefpial  elevation,  a  kind  of  wide  trouf^h  or  synclinal  fold 
or  riepression  appears  to  ha\'e  been  formed  between  the 
middle  and  eastern  part  of  America,  which  was  at  first 
occupied  by  a  wide  arm  of  the  sea,  later,  by  continued 
elevation,  by  a  great  body  of  fresh  water,  and  later  by  low 
marshes  and  low  marshy  islands  barely  above  sea-level. 
Up(jn  these  low  lying  lands  grew  a  dense  vegetation  unlike 
any  of  the  pr  sent  day,  but  resembling  somewhat  the  tree 
ferns  of  our  southern  semi-tropical  States.  This  low  lying 
region  was  subject  to  freshets  and  inundations  from  the 
surrounding  higher  regions,  periodically  deluging  the 
swamps  and  swamp  vegetation  with  liver  and  flood  deposits 
of  pebbles  and  sand,  under  pressure  (jf  which  the  peat 
gradually  turned  into  coal.  Successive  coal  seams  were 
formed  by  successive  growths  of  vegetation  bi  ween  the 
intervals  of  periodic  inundation,  or  of  subsidence  and 
possibly  at  times  of  upheavals,  for  these  low  lands,  as 
sediments  accumulated,  appear  at  times  to  have  sunk  below 
the  sea  and  again  to  ha\'e  been  either  built  up  abo\'e  it  by 
fresh  supplies  of  sediment,  or  to  have  been  temporarily 
raised  up  by  upheaving  forces. 

Finally  by  a  grand  revolution  which  closed  the  Carbonif- 
erous age  in  America,  the  coal  swamps  with  their  coidbeds 
and  strata  were  crumpled  up  to  form  the  present  great 
Appalachian  Chain. 

Similar  movements  no  doubt  took  place  about  the  same 
time  in  the  Rocky  Mountain  and  Western  region.  But 
here  the  marine  condition  seerns  to  have  predominated 
over  the  fresh  water  one,  for  we  find  the  Carboniferous  in 
Colorado  more  represented  by  marine  fossiliferous  lime- 
stones and  sandstones  than  by  those  of  fresh  water  origin, 
though  the  Weber-grits  may  have  had  a  fresh  water  origin, 
as  in  a  few  rare  instances  we  find  fossil  plants  like  those  in 
Pennsylvania  together  with  a  few  insignificant  small  seams 
of  coal.     But   in  the  West  it  is  evident  that  the  circum- 


I' 

4 


stances  from  one  cause  or  another  were  not  favorable  for 
the  production  and  f,^rowth  of  extensive  coal-beds  as  in  the 
Eastern  States.  The  coal  forniinjif  time  was  reserved  in  the 
West  for  a  much  later  period,  vi/.:  the  Laramie  or  l'p|)er 
Cretaceous.  The  Lower  Carboniferous  in  Colorado,  how- 
ever, contains  in  its  limestones  much  of  our  silver-lead 
wealth  as  at  Leadville  and  Asjien. 

The  Cambrian,  Silurian.  l)evonian,  and  Carboniferous 
Af,^es  have  been  grouped  toj.jether  by  j^-eoloj^ists  into  one 
great  era,  the  Paleozoic,  owing  to  a  general  family  likeness 
in  the  fossil  fauna  and  flora  of  these  ages. 

To  the  Arcluean  and  Paleo/oir  rocks  the  bulk  of  our 
veins  and  deposits  of  gold  and  siher  are  mainly  confined, 
thouc^h  both  in  Colorado  and  elsewhere,  as  will  appear 
later  if  certain  peculiar  conditions  are  present,  the  rocks  of 
the  later  and  newer  periods  may  also  in  some  regions 
produce  precious  ores.  Hut  the  prospector  should  gi\'e  his 
closest  attention  to  these  older  rocks,  hence  we  have  de\'oted 
extra  space  to  their  (iescription  anrl  history. 

TRIASSIC   AND   JURASSIC,    OR  JURA-TRIAS. 

Aft^r  the  Carboniferous,  followed  the  Triassic  and  Ju- 
rassic; sometimes  in  America,  owing  to  the  didiculty  of 
positively  separating  the  two  periods,  they  are  combined 
under  one  name,  the  Jura-Trias,  and  in  Colorado  are  locally 
called  the  "  Red-Beds,"  owing  to  their  prevailing  red  and 
variegated  colors.  The  series  is  well  represented  in  the 
celebrated  Garden  of  the  (lods,  near  Colorado  Springs.  The 
red  conglomerate  sandstone  of  the  Trias  proper,  has  so  far 
yielded  no  determinative  fossds,  but  the  variegated  clays 
in  the  upper  Jurassic  at  Morrison  and  elsewhere  have 
yielded  some  remarkable  Saurian  remains  of  land  lizards. 
It  is  probable  from  the  presence  of  salt  and  gypsum  in 
these  red-beds,  and  the  prex'ailing  redness  of  the  rocks,  due 
to  iron,  which  was  not  leached  out  through  the  agency  of 
organic  life,  and  the  general  absence  of  fossil  remains,  that 
the  lower  portion  of  these  rocks  was  laid  down  in  land- 
locked salt  seas,  or  salt  lakes,  shunned  by  both  vegetable 
and  animal  life.  The  upper  portions,  however,  show  evi- 
dence of  the  existence  of  land  of  a  low  marshy  character, 
with  fresh  water  and  probably  large  estuaries,  as  we  find  the 
remains  of  turtles,  crocodiles,  fresh  water  shelh.  and  Dino- 
saurs or  land  lizards.  The  rocks  of  these  periods  are  not 
generally  prolific  in  ores.    The  Silver  Reef  sandstone  of 


33 

rtah  is  :in  exception,  which  contains  chloride  of  silver 
(lisseniinated  throuifh  it.  When  piercerl  hy  eriipti\e  rocks, 
however,  ore  should  be  looked  for  in  this  series  as  else- 
where. 

CRKTACF.OUS  I'KRIOD. 


V 


this   followed   the   Cretaceous,   a    series    of    very 


I'pon 
thick  formations,  numbering  several  thousands  of  feet  in 
Colorado,  consistinf^  in  its  middle  portion  of  limestones,  and 
thick  beds  of  drab  shale.  These  are  mostly  marine,  as 
shown  by  the  sea  shells  in  them,  but  at  the  base  is  what  is 
called  the  Dakotah  group  or  Cretaceous  No.  i,  a  prominent 


Platf.  VI. 

North  America  in  the  Cretaceous. 

sandstone  hogback  in  which  the  fossil  impressions  of  leaves, 
very  like,  but  not  identical  with  those  of  the  jiresent  day,, 
show  that  land  and  fresh  water  existed  at  the  time.  The- 
limestones  and  clays  of  the  middle  or  Colorado  group,, 
contain  cjuantities  of  fossil  marine  shells,  such  as  the 
Nautilus,  Ammonite,  Baculite  and  Inoceramus. 

The  Laramie  forms  the  upper  group  of  the  Cretaceous, 
and  contains  our  principal  western  coal  fields  and  abounds- 
in  fossil  remains  of  tropical  foliage. 

This  Laramie  group  marks  an  important  era  in  our  Rocky 
Mountain  region  for  it  shows  that  beginning  of  the  great 
Rocky  Mountain   revolution,  by  which  the  granite  islands 


1' 


^"rmaBOrttfcSaS^iiaiatB 


34 

before  mentioned,  against  which  all  the  previous  sediments 
had  been  forming  mainly  beneath  the  sea,  were  elevated 
lo.ooo  feet  or  more  into  continental  or  mountainous  masses, 
dragging  up  with  them  portions  of  the  sea  bottom  and  ex- 
posing it  as  land  surface,  dr  i.uing  otT  the  shallow  Creta- 
ceous sea  which  had  hitherto  divided  the  Eastern  half  of  the 
American  continent  from  the  Western,  bringing  on  a  land 
and  continental  condition,  which  was  com))leted  in  the  fol- 
lowing Tertiarv  age  and  has  continued  to  the  present.  See 
plate  VI. 

The  Jurassic,  Triassic  and  Cretaceous  are  grouped  into 
one  main  division  called  the  Mesozoic  or  middle  life  era  of 
the  world's  history.  None  of  the  rocks  of  this  age  in  Col- 
orado are  celebrated  for  ore  deposits,  e.xccpt  locally  under 
local  conditions. 

In  California  and  portions  of  the  extreme  West  where 
these  rocks  have  been  highly  metamorphosed  by  heat  and 
penetrated  by  igneous  rocks,  some  of  the  leading  ore  de- 
posits of  gold  and  silver  are  found.  The  same  remark 
applies  also  to  the  succeeding  Tertiary  in  those  regions, 
particularly  in  the  Sierra  Ne\ada  and  Coast  ranges. 


i 


^     !\ 


■    ./.:  TERTIARY. 

The  Tertiary  age  seems  in  the  Rocky  Mountains  to  mark 
an  era  of  comparative  rest  in  mountain  elevation,  for  the 
strata  forming  some  of  the  divisions  of  this  age  lie  ahuost 
horizontally  upon  the  tops  of  the  earlier  upturned  periods. 

These  beds  were  formed  by  fresh  water  lakes  'm  Colorado 
surrounded  by  tropical  \'egetation.  In  the  Coast  ranges  of 
California  the  Tertiary  is  upturned  into  mountain  forms  and 
metamorphosed,  and,  from  the  presence  of  sea  shells,  is 
clearly  of  marine  origin.  The  Tertiary  in  Colorado  is  best 
seen  in  outlying  table  lands.  In  Wyoming  the  Tertiary  lake 
formed  the  Careen  River  beds  and  Bad  Lands  abounding  in 
fossil  mammals,  leaves,  fishes  and  insects.  The  Tertiar\' 
was  the  world's  tropical  summer,  a  period  of  beautiful  lakes 
of  semi  tropical  foliage  and  a  warm  climate.  In  certain 
regions  it  was  disturbed  by  gigantic  revolutions  which  up- 
heaved the  Himalayas  and  the  Alps.  Such  revolutions  as 
occurred  in  our  Western  Cordillera  svstem  were  marked  by 
enoruKJUs  ebullitions  of  lawis  of  various  kinds  issuing  fr<jm 
fissures  deluging  Idaho,  Nevada,  part  of  Oregon,  and  Wash- 
ington. Remnants  of  this  same  disturbance  are  seen  in  the 
form  (;f  basaltic  ox'erflows  cajiping  Tertiary  strata  in  Colo- 


35 

rado  and  New  Mexico;  and  the  vast  V(ilcanic  region  oi  San 
|uan  in  Southern  Colorado  is  covered  with  successive  lava 
()verflows  of  the  same  period. 

The  Tertiary  rocks  in  Colorado  arc  not  generalh-  good 
prospecting  grounds.  The  lavas,  however,  are  (with  the 
exception  of  the  basalt,  which  for  some  reason  is  generally 
sterile)  locally  productive,  as  for  instance  the  entire  San 
fuan  Region,  also  Cripple  Creek  Mining  Camps  and  Silver 
Cliff.  So,  the  prospector,  whilst  he  need  not  Avaste  time 
among  the  sedimentary  beds,  will  do  well  to  examine  any 
eruptive  rocks  of  this  period  for  gold  especially,  and  also 
for  silver.  The  varieties  of  lava  are  principally  andesite, 
rhyolite,  trachyte  and  basalt.  In  the  Coast  range  of  Cali- 
fornia where  the  Tertiary  beds  have  been  metamorphosed 
by  heat  into  slates,  gold  and  cinnabar  are  found. 


(II.ACI.AI,    EPOCH    AND   QUATKRNARY    AGK. 

The  Tertiary  Summer  was  closed  by  the  world's  Great 
Winter.  The  ice  from  the  north  pole  for  some  reason  we 
will  n(^t  discuss,  extended  its  domain  far  south  to  latitude 
40.  All  the  northern  temperate  regions  of  the  world  were 
ice-sheeted  and  the  sheet  extended  itself  as  by  long  fingers 
down  the,  by  that  time,  highly  de^^eloped  mountains,  filling 
the  ravines  with  glaciers.  By  the  downward  destructive 
grinding  motion  of  the  glaciers,  the  ravines,  commenced 
by  water,  were  deepened  and  widened  by  ice.  Fissure  veins 
were  thus  exposed,  both  of  gold  and  silver.  The  debris 
from  their  progress  the  glaciers  carried  on  their  backs  and 
dumped  at  the  outlet  of  the  canyons;  and  when  the  tem- 
perature finally  became  warmer,  and  the  glaciers  melted,  all 
the  long  lines  of  traveling  boulders  scattered  upon  their 
backs,  many  of  them  containing  gold  r<3bbed  from  the  veins. 


were    left   as   banks    or    "moraines 


forming 


our 


srold 


placer"  grounds  alongthe  sides  of  our  streams  and  canyons, 
or  sometimes  a  thousand  feet  abo\'e  the  present  river  bed, 
marking  the  original  height  or  thickness  the  great  ice  bodies 
once  attained. 

So  were  our  canyons  largely  formed,  and  so  did  our  gold 
placers  originate.  After  the  Glacial  Epoch,  a  warmer  peri(xl 
set  in,  called  the  Ouaternary.  The  ice  melted.  Vast  bodies 
of  fresh  water  were  distributed  in  wide  streams  and  mon- 
strous lakes  over  large  portions  of  this  hemisphere.  The 
nnigh  "  morainal  "  dumps  of  the  glaciers  were  "sorted  "  or 
"modified  "  by  water,  rolled  into  pebbles  and  sand,  .md  re- 


clistributed  iihnv^  the  banks  of  streams  or  carried  out  into 
beds  oi  lakes.  In  these  pebbles  and  sand,  was  much  of  the 
precious  metal  mined  and  nibbed  from  the  veins.  The  gold 
by  its  insolubility  remains  to  this  day  in  our  placer  beds  and 
■"'drift"  or  "wash"  and  is  collected  by  hydraulic  mining. 
That  the  prospector  for  gold  should  closely  study  these 
Glpcial  and  Ouaternary  deposits  is  evident. 

So  ends  the  history  of  our  section.  Still  the  agencies  of 
nature  are  at  work  as  of  old.  Continents  are  gradually 
rising  or  sinking.  Mountains  are  being  imperceptibly  ele- 
vated. Water  is  still  sculpturing  them  with  canyons. 
Rivers  are  carrying  down  fragments  robbed  from  the  land 
and  depositing  them  in  the  cjcean  to  form  strata  for  future 
•continents. 

The  fires  of  the  earth  are  not  yet  dead,  for  volcanoes  still 
vomit  lava.  The  earth,  hoviver,  is  still  continuing  to  lose 
internal  heat.  Its  crust  is  still  contracting  and  wrinkling 
itself  upwards,  for  we  find  modern  sea  beaches  raised  high 
■on  our  seaboard  cliffs.  Shocks  of  earthquakes  from  time  to 
time,  prove  that  motion  of  some  kind  is  going  on  beneatli 
us,  and  doubtless  our  mountains  are  still  rising  imper- 
ceptibly, as  they  appear  to  ha\'e  done  in  ages  past,  gi\  ig 
additional  lifts  and  elevation  to  old  uplifted  strata,  and 
slowly  elevating  newer  strata  that  since  the  Tertiary  have 
lain  apparently  undisturbed.  We  say  apparently,  for  not 
onlv  are  the  Tertiar\'  beds  uplifted  from  5  to  10  degrees,  but 
even  the  more  recent  Ouaternary  deposits,  showing  that 
movement  has  been  going  on  comparatively  recenth'  and 
may  still  be  progressing  imperceptibly. 


CHAPTER  III. 


I 


THE    PROSPECTOR'S    PALEONTOLOGY    OR     STUDY    OF 

FOSSILS. 

A  prospector  in  his  roaming  among  the  rocks  is.  likely 
from  time  to  time  to  come  across  a  good  many  fossils  or 
petrified  remains  of  life  that  once  existed  on  this  planet. 
He  will  feel  curious  to  know  what  these  are,  what  class  of 
animal  or  vegetable  they  may  represent,  to  what  geological 
era,  epoch,  or  subdivision  they  may  belong. 


CHAMCTERI5TIC 


Rocks.        M:meral5,  Metals  ^c.      Fo  15/ l5. 


^mM^Mtim  Pebbles  Sand,  CI  ay 


iV,iMiJi 


I'  I' '  '  ' 


«*^^ 


'decent 


I 
I 


iardmie 


% 


Soil. Clay,  Pewes 


Loo5ely  srratified 
Conglomerdtex-5dnd5 

Bmit  flndesite 
Rnyol/te  Ldva^ 
conglomerdtes 

sandstones 
•5hdle6  ^  C/dys 

Some  or  i/b/canic 
detritus,  others  of 

Granitic  detritus 


^f' 


-_   Beds 
■5ancl3rones 

Drab.  .5 hales.  C/ays 

Littie^totie 
Dark  Shales 
(Mdlomerdte  oandstone 


Goal 

dnonCh)' Oil  Horizon 
Flux  LItne 

Clay,  /ron,5tone 
r/re  Cidv 


"one 


Thin  Limestones 
T/iicKRedConglometate 
sandstone 


Gyfuiferous  J/?ales 

Reddish  Cnnglomerate 

faslern  Coal  Beds 

Shales, ^andslones 
Grits  a  Shales 


Blue  Limestone 


Reddish  Sandstone 
Limestones 


Drab  Pale  Limestone 
Dolomite 


Elates 
Quartzites 


Oudrtzite^,  cofjglomeritic 
GneiJ5,Jchisr 
States,  i\4arbte 


Granite,  Gneiss 
Schist  Syenite 


3o me  Gold 


Placer  Gold 


Old  Gold  Placers 

it!  California 

Ldva-Goid0ikrl>minQ 
Thin  Lignite  codl 
Metamorphosed Sdndstcnt 

.  Gold  bearing 
m  California  also 
flshphalt 

in  Colorado 
andCalifotnia 


Gypsum 
Oil  and  Lime  & 
Md  Building  3rone 


^  Copper 
j/l/ca  forG/as5 
Silver.  Reef  Sanablone 
5omeffailB/Jilcling  Stone 


Eastern  Coat 
of  Pennsylvania 

Silver.  Lead 


futeka.  Nevada 
Silver  Lead 

Deposits 


t^arbte 

Jitver.  Lead 

Iron 


Gold 


Gold.  Olivet 
LeadZittcCopper^c. 

Iron 


i^an.  But  halo  Be. 


Elepiiantsteetii^Bones 
Man  Bones,   Tools 


Fo55il  Leaves 
Afammals 

in  California 
/iilarine  Shells 


team.  Trees  3c. 
sea  Shells 

Scdphites  Baculites 

Sea  Shei/s 

inocergmus 

oyjters 
Leai^es  of  Trees 


Dinosaurs  Colo. 
SeaSheits/nl^o/mng 


fwtprintsofJdurtans 


Land  Plants 

Corals 
Sea  Shells^  Spin fers,etc 


SeaShetts 
Fish  Corals 


JeaShettj 
Crustacea 
Tri to  bites  Corals 


JeaMb 


FetvPostttve 
J/g/7sofLtFe 


Plate  VII. 

Prospectors'  Geological  Table  of  Wesiern  Formations,  Showing  Principal  Characteristic  Rocks, 

Minerals  and  Fossils  to  be  Found  in  Them. 


i:  \\ 


I 


38 


li 


Fossils  to  a  geologist  arc  the  labels  of  the  rocks;  show 
a  geologist  a  fossil,  and  he  will  probably  be  able  to  tell  at  a 
glance  whether  the  fossil  came  from  a  series  of  Paleozoic, 
Mesozoic  or  Ceno;:oic  rocks,  whether  it  belonged  to  a  ver}- 
ancient  geological  period  down  near  the  primitive  granite, 
or  to  a  comparatively  recent  one  near  the  modern  soil,  high 
up  in  the  geological  scale  and  nearer  to  the  life  of  the 
present  day.  He  mav  be  able  to  tell  not  merely  whether 
it  belongs  to  one  of  the  great  divisions,  to  the  great  eras, 
but  also  to  the  subdivisions  of  these  eras,  whether  to  the 
Silurian  or  Carboniferous,  the  Jurassic  or  the  Cretaceous, 
or  even  to  minor  divisions  of  these,  called  groups  ;  whether, 
for  example,  it  belongs  to  the  Dakotah  group  of  the  Creta- 
ceous, or  to  the  Laramie  group  of  the  same  period. 

PRACTILAI-   USE   OK    FOSSIL.S. 

The  practical  use  of  a  general  knowledge  of  fossils  is 
obvious.  A  prospector  linds  in  certain  strata  a  fern-leaf 
of  the  Carboniferous,  this  tells  him  he  nmst  be  on  the 
coal  strata  and  forthwith  he  hunts  for  coal.  Or  he  linds 
a  Paleozoic  shell  or  coral  which  points  to  the  fact  that  he  is 
probably  in  the  neighborhood  of  the  precious  ore-bearing 
rocks. 

Later  perhaps  he  finds  a  shell  or  ccal  characteristic  of  the 
lower  Carboniferous  blue  liniest<jne,  the  celebrated  lead- 
silver  bearing  formation  of  Colorado  and  the  West,  and  he 
is  encouraged  to  look  for  these  ores.  The  limestone  by 
itself  is  but  a  poor  guide,  for  there  are  many  limestones  not 
unlike  it  in  the  different  series  of  rocks,  but  this  particular 
shell  labels  this  as  " //le  blue  limestone"  and  no  other. 
Hence  a  chai"acteristic  fossil  may  help  considerably  in  fol- 
lowing up  in  its  extension  an  ore-bearing  rock,  and  not 
only  that  locally,  but  in  regions  very  far  apart.  Soon  after 
the  celebrated  ore  deposits  of  Aspen  were  disco\ered,  and 
thf"  mines  were  in  their  infancy,  some  fossils  were  discov- 
ered that  showed  the  deposits  to  be  in  the  same  limestone 
as  that  at  Leadville,  which  had  proved  there  so  productive. 
This  gave  an  additional  impetus  to  the  camp,  "  a  second 
Leadville  "  so  it  was  said. 

Again,  though  a  prospector  may  not  find  at  once  the  par- 
ticular geological  stratum  or  period  he  is  looking  fcjr,  it  he 
finds  a  characteristic  fossil  anywhere,  in  some  other  period, 
he  knows  from  it  whether  the  period  he  is  after  lies  geologic- 
ally belo^^  or  above  where  he  is  lo(jking. 


1 


39 

Thus,  if  a  prospector  finds  a  Silurian  shell  he  knows  that 
the  Carbonilerous  "  blue  limestone  "  must  be  close  abo\'e 
this  Silurian,  or  if  he  finds  a  Marine  Cretaceous  shell,  he 
knows  that  the  Laramie  coal-bearinj^  group  lies  above.  On 
finding-  a  Cretaceous  or  Jurassic  fossil,  he  knows  that  the 
Carboniferous  and  Paler^zoic  series  must  lie  considerably 
below  him. 

In  the  accom^.anying  geological  table,  Plate  VII,  we  have 
shown  what  rocks  and  what  minerals  and  metals  are  likely 
to  he  found  in  the  geological  divisions  and  subdivisions ; 
also,  generally,  what  classes  of  fossil  life  are  to  be  expected 
in  each. 

Then  in  the  diagrams  of  fossils,  we  have  selected  pictures 
of  the  fossils  most  commonly  to  be  found  in  all  the  great 
divisions,  so  that  if  the  prospector  finds  a  fossil,  he  may,  by 
comparing  it  with  the  pictures,  find  what  its  name  is,  and 
to  what  great  geological  division  or  subdivision  it  belongs  ; 
it  is  not  so  necessar\'  for  him  to  remember  the  scientific 
"jaw-breaking"  names  of  these  fossils,  as  it  is  for  him  to 
be  able,  at  sight,  to  recognize  whether  it  belongs  to  one  or 
other  of  the  great  eras,  or,  better  still,  to  one  of  the  minor 
subdivisions  of  these  ;  whether  it  is  Paleozoic  or  Mesozoic, 
whether  Silurian  or  Cretaceous,  whether  it  belongs  to  the 
Colorado-Marine-Cretaceous  or  to  the  Laramie  fresh-water 
Cretaceous,  etc.  If  the  fossil  is  a  very  peculiar  one  and  can 
not  be  identified  as  belonging  to  any  of  the  common  ones 
we  have  pictured,  he  had  better  send  it  to  the  office  of  the 
U.  S.  Geological  Survey  at  Washington,  or  to  some  good 
paleontologist.  We  frequently  have  fossils  sent  to  us  to 
know  whether  this  or  that  fossil  is  a  likely  indication  of  the 
presence  of  coal  ov  other  mineral,  and  sometimes  our  iden- 
tification is  a  material  help  to  the  prospector;  but  with  the 
above  table  the  prospector  could  save  himself  the  trouble 
and  postage'  stamns. 

■      -H 

ARCHAEAN. 

Starting  then  from  the  Archaean  as  a  sure  and  safe  hoii- 
zon.  the  prospector  will  find  no  fossils,  and  only  some  in- 
direct probable  evidences  of  past  life,  such  as  graphite, 
which  may  possibly  represent  ancient  coal  derived  fron 
some  form  of  vegetation  unknown  to  us.  Limestone  and 
marble  are  also  indirect  evidences  of  past  organic  life,  most 
modern  limestones  being  due  to  the  remains  of  corals,  etc. 
Whatever  life  may  have  existed  in  those   primitive  granitic 


ffT 


40 


i 


rocks,  has  been  pretty  well  obliterated  by  excessive  meta- 
morphism  and  crystallization  of  the  strata. 


CAMBRIAN. 


Resting  on  the  granite  he  finds  the  "Primordial"  or 
"Cambrian"  series,  sometimes  called  the  Potsdam  Sand- 
stone. If  this  series  consists  of  unaltered  sandstones,  he 
may  be  fortunate  enough    to   find   some  of  the  shells  and 


Plate  VIII. — Cambrian  Fossils. 

I,  2,  3,  I'lilobites ;  4,  Track  of  Crustacea  ;  5,  Track  of  Worm  ;  6,  7,  Sea  Shells. 

other  traces  of  life  of  those  old  beaches  as  shown  in  the 
diagram,  but  generally  speaking,  in  Colorado  and  the  West, 
the  Cambrian  is  so  highly  metamorphosed  and  altered  into 
hard  crystalline  quartzites,  that  evidences  of  past  fossil  life 
are  as  scarce  and  indistinct  as  in  the  Archaean,  and  probably 
for  the  same  reason.  The  forms  he  may  find  are,  a  little 
Crustacea  called  a  Trilobite,  something  like  a  "  sand  crab," 
also  a  few  little  shells  and  some  marks  of  worms.  Plate 
VIII. 


41 


SILURIAN. 


In  the  next  series,  the  Sihirian,  he  may  be  more  fortunate. 
He  may  find  remains  of  sea-weeds,  corals  and  shells  and 
fragments  of  a  sort  of  sea-worm  called  a  Crinoid,  or  sea  lily. 
The  little  discs  with  a  hole  in  the  center  forming  a  little 
ring  about  the  siice  of  a  pea,  constituting  the  discs  or  rings. 


10 

to 

fe 

ly 

,le 

t>. " 
te 


Plate  IX.  -Silurian  Fossils. 

I.  2,  Orthis  ;   -^   4,  Spirifer  ;   5,  Pleurotomaria  ;  6,  Murchisonia  ;  ja,  ji,  Trilobite 

(Calyniene) ;  8,  Coral  Fenestella  ;  g,  Coral  Choetites  ;  10,  Graptolite; 

II,  Orthoceratite. 

of  which  the  stems  of  the  sea  lily  are  composed,  are  some- 
times very  common  in  Silurian  and  Paleozoic  rocks,  though 
it  is  rare  to  find  a  complete  Crinoid,  and  especially  the 
beautiful  comb-like  flower  or  head  of  the  sea  lily.  He  is 
likely  to  find  also  a  more  advanced  type  of  the  Trilobite  and 
various  Spirifers  and  other  shells  as  pictured.     Plate  IX. 


I 


\^ 


I.  i 


42 

DEVONIAN. 


In  the  Devonian  he  may  fnul  the  teeth  or  bones  of  fishes, 
and  a  tew  remains  of  pcciiUar  land  phmts,  neither  of  which 
are  known  in  the  Silurian  below,  also  many  corals. 


Plait,  X.— Devonian  Fossils. 

I,  Spirifer  ;  2,  Comoc.Trdiuin  ;  3,  Orthis  :  4,  Goniatites  ;  5,  6,  7,  Corals  ;  8,  g,  10, 
Fish  'ieeth  ;  11,  12,  Fish  Scales. 


CARBONIFEROUS. 

In  the  Lower  Carboniferous  "blue  limestone,"  corals  and 
shells  appear,  especially  vSpirifers  and  Productus,  together 
■with  Crinoids  and  a  \ery  simple  curled  shell  like  a  snake 
coiled  up,  a  "  Goniatite,"  one  ot  the  earliest  of  the  Ammonite 
class.  At  Aspen,  associated  with  the  ore  deposits  we  f(nind 
in  the  blue  limestone  most  of  these,  tcjgether  with  a  kind  of 
snail  shell  called  Pleurotomaria.    At  Leadville  in  the  same 


ili 


43 


lonnation  Spirifers  and  Productus  are  occasionally  found. 
A  very  curious  C(jral  is  one  shaped  like  a  screw,  called 
Archimedes,  alter  the   author  (^f   the   screw.     Cup  corals 


are  common. 


<IIU    L.OI11II1WII. 

In  the  Middle  Carboniferous,  associ.;ted  with  the  coal 
seams,  many  curious  remains  of  rteds,  ferns  and  other 
a(|uatic  plants  ol  that  aj^e  are  found,  but  these  are  scurce  in 
Colorado  and  the  West.    The  prospector  will  ob;:;rve  that 


Plate  XI.— Carboniferous  Fossils. 

Ill,  il>,   ic,  Productus;  2,  2,  Spirifers;  ;:i,  3,  3,   Rhyiiconell.-i ;_  4,  Euomphalus  ;  5,  5, 
Crinoids  ;  6,  Pleurotom.iri.i ;  7.  Bellerophdii  ;  8,  Athyris  Subtilita  ;  g, 
Astartella  ;  10,  Ocmiatites  ;_  11,  12,  Corals;  13,  14,  15,  16, 
Plants;  17,  Spine  of  Echinus. 

there  is  a  general  family  likeness  between  the  fossils  of  each 
division  of  the  Paleozoic  and  in  the  Paleozoic  as  a  whole, 
and  it  may  not  always  be  easy  for  him  to  determine  whether 
a  shell  is  Silurian,  Devonian,  or  Carboniferous,  but  of  one 
thinjT  he  will  be  certain,  that  it  is  Paleozoic. 


IP! 


^l 

% 


i 
III 


44 


TRIASSIC. 

In  the  Trias  throughout  the  West,  he  is  not  Hkely  to  find 
inanv  fossils,  the  locks  are  generally  too  coarse,  but  in  the 
Eastern  States,  though  he  may  n(jt  find  any  true  remains, 
he  mav  observe  the  tracks  left  by  great  Saurians,  as  they 
walker!  on  their  hind  feet,  or  on  all  fours,  on  the  red  sands 
of  the  beaches  of  those  dreary  salt  Triassic  seas,  leaving 
"  footprints  on  the  sands  of  time  "  full  of  interest. 

JURASSIC. 

In  the  lurassic  shales  and  limestones  in  Colorado,  he  may 
be  equally  unsuccessful,  though  in  the  upper  Jurassic  just 


"^^yx 


PlATK   XII. — JURA-TRIAS    FOSSILS, 

1,  Dinosaur  Lizard;  2,  3,  Foot  and  Shoulder  Bone;  4.  4,  Vertebra  of  Sea    Saurian, 

Ichthyosaurus  ;  5,  6,  6,  Teeth  of  Saurians  ;  7,  Belemnite  ;  8,  Echinus 

9,  9,  Ammonites;  10,  Exogyra  ;  11,  Trigonia  Shell. 

below  the  Dakotah  sandstone,  he  may  light  on  the  bones  of 
gigantic  Dinosaurs,  or  great  land  lizards,  such  as  the  author 
found  in  Colorado  and  Wyoming,  monsters  60  to  80  feet  in 
length  and  proportionally  tall,  standing  from  20  to  25  feet  in 
height.  In  the  lower  Jurassic  in  Wyoming,  he  will  find 
great  numbers  of  sea-shells  and  Ammonites,  and  a 'round 


4S 

shell  like  a  cigar  called  a  "  Hclemnite  "  or  spear-fiearl.  thc- 
internal  shell  of  an  ancient  cuttie  tisli.     Plate  Xll. 


CRETACEOUS. 


In  the  Cretaceous,  bej^inning  with  the  lowest  group,  the' 
Dakotah  group,  net-veined  leaves  of  deciduous  trees,  such 
as  the  willow,  <n\k,  maple,  etc.,  the  earliest  known  lea\es  of 
those  kinds  of  trees,  may  be  expected  in  the  sandstone  anrt. 
clays. 


Plate  XIII.— Cretaceous  Fossils. 

I,  I,  Inoccramus  ;  2,  Cardium  ;  3,  Corbula  ;  4,  Mactra ;  5,  Margarita  ;  6,  Fasciolaria  ;: 
7,  Anchura  ;  8,  Pyrifusus  ;  g,  10,  Sc.iphites  ;  11,  Criocera'. ; 
12,  Baculites  ;  13,  Shark's  Tooth. 

In  the  Colorado  group  of  the  Cretaceous,  above  the 
Dakotah,  abundance  of  oyster  shells  and  large  clam  shells 
(Inoceramus)  are  sure  to  be  found  in  the  limestones  and 
marine  shales.  In  the  Montan,  group  of  the  Cretaceous 
above  this,  consisting  mainly  of  drab  shales  and  some  sand- 
stones, great  quantities  of  sea-shells  are  found,  amongst 
them  various  peculiar  forms  of  the  Ammonite  allied  to  the 
modern  nautilus,  and  called  Scaphites,  resembling   snakes^ 


46 

(jr  worms  uncoiling?,  together  with  shark's  teutli  and  bones 
of  sc;i  Saiirians. 

In  tin-  sandstones  of  the  Laramie  Cretaceous  remains  of 
sea-weeds  are  found;  in  tlie  sandstones  immediately  below 
the  coal-beds,  and  in  those  associated  with  or  above  the 
coal,  are  found  ^neat  varieties  of  semi-tropical  leaves,  such 
as  those  oi  the  j)almetto.  i\^.  beecii,  elm,  magnolia,  sassafras, 
etc.  The  presence  of  these  leaves  is  a  pretty  sure  indica- 
tion of  coal. 

Ti;i<ri.\K\. 

In  the  Tertiary  fresh-water  beds,  similar  lea\'es  and  thin 
beds  of  poor  lignite   C(jal  are   found,  together  with   fossil 


Plate  XIV. — TKR'nAkv  Fossii.s. 

I,  Palmetto  ;  2,  ("innamon  Leaf;  3,  C.irdium  ;  4,  Insect  ;  5,  Nutnmulite  Shell ; 

6,  7,  Fresh-Water  Shells. 

gUATKRNARY     FOSSILS. 

8,  Mammoth  Elephant's  Tooth  ;  9,  Mastodon's  Tooth  ;  10,  Flint  Implement; 
II,  Stone  Grooved  by  Glacier. 

insects  and  remains  of  mammals.     In  the  Marine  Tertiary 
are  sea-shells. 

QUATERNARY. 

In  the  Quaternary  drift,  amongst  the  pebbles,  sands  and 
"wash"  characteristic  of  g(jld  placer  beds,  an  occasional 
tooth,  tusk,  or  bone  of  the  great  hairy  Mammoth  elephant 
or  the  Mastodon  elephant  may  be  discovered,  together  with 
the  stone  implements  or  bones  of  prehistoric  man  and 
pebbles  grooved  h\  glaciers. 


47 

CHAPTER  IV. 

THE  PROSI'FXTOR'S  LITllOLOC.Y  OK  STUDY  Or  ROCKS.. 

A  prospector  wants  to  know  a  jj^rcat  deal  about   rocks. 
They  are  his  constant  lonipanions  in  the  field.     Ilis  busi- 


l 

> 

a 

— 

n 

T" 

a 

.§ 

VI 

^ 

7i 

% 

1 

V 
n 

o 

H 

I 

•0 

> 

I 

> 

s 

r. 

■0 

^ 

T* 

^> 

X 

u  vi 

rt  s* 

y 

■J.    3 

-    % 

^ 

^5? 

r. 

t^S 

U' 

OS 

^ 

is^ 

> 

D     -? 

n 

ii-a 

> 

^=r 

•/ 

r. 

?r 

- 

o 

"T" 

c 

PC 

n 

o 

(~ 

&5 

r. 

i^ 

J. 

W 

X 

p 

t 

.^ 

r» 

K 

(^ 

tt; 

P 

•a 

^ 

^ 

M 

c 

a 

ncss  is  amongst  rocks.     He  wants  to  be  able  to  recognize 
them  at  sigiit,  when  he  picks  up  a  loose  pebble,  or  confronts 


! ; 


■/% 


//..■ 


"'^^vc^/' 


rr^" 


X 

v. 


t^" 


>< 


//\ 


^ 


•^  ;• 


^/. 


V. 


■v-i 


-v^i 


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a  mighty  cliff.  When  travelUng 
ON'cr  the  mountains,  as  he  sur- 
veys the  grand  panorama  from 
the  top,  he  wants  by  the  pecuhar 
forms  and  patterns'  each  variety 
of  rock  is  apt  to  take  as  the  re- 
sult of  erosion  and  weathering 
owing  to  different  degrees  of 
hardness,  to  be  able  to  make  a 
shiewd  guess  from  a  long  dis- 
tance, as  to  whether  one  moun- 
tain is  made  of  granite,  or  another 
of  limestone,  ^r  a  third  of  por- 
phyry. This  liabit  of  forming 
rough  guesses  as  to  the  charac- 
ter of  distant  rocks,  decides  him 
as  to  choosing  his  course  for 
prospecting.  "  In  those  sharp 
granite  looking  peaks  "  he  says, 
"may  be  1  will  find  fissure  N'cins. 
Yonder  cones,  like  the  spires  and 
minarets  of  a  Gothic  cathedral 
must  be  porphyrj'  or  igneous 
rock,  another  likely  localit}',  and 
mark  where  they  break  through 
the  sedimentary  strata,  and  tip 
them  up  ail  around  them  ;  at  the 
junction  of  these  sedimentaries 
with  the  igneous  rock,  there  may 
be  lime-stone,  and  a  '  contact 
blanket  deposit."  Von  smooth 
grassy  slopes  are  probably  under- 
laid by  sandstone  or  limestone, 
and  the  rolling  valley  beneath  by 
soft  shales.  The  latter  are  un- 
promising for  precious  ores."  Or. 
again  descending  from  his  perch 
into  the  canyon  below,  he  recog- 
nizes the  granite  basis,  and  on 
top  of  it,  a  series  of  sedimentary 
rocks.  The  lowest  of  these,  by  its 
rust3'-white,  masonry-like  struc- 
ture, lie  judges  to  be  Cambrian 
(piartzite,  the  thin-bedded  strnta 
above,    Silurian   limestones,   and 


^^ 


49 

the  heavy  massive  beds  above  these,  Lower-Carboniferous 
blue-limestone,  whilst  a  dark  greenish-gray  rock,  running 
in  and  out  irregularly  among  the  strata,  sometimes  between 


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LINCOLN 


I^HlTt  P 


the  stratification  planes,  at  others  cutting  across  tiiem,  he 
judges  to  be  an  intrusive  sheet  of  p(irjihyry.  and  looks  again 
f(jr  "contact  deposits."  A  rock  running  up  like  a  low  wall 
from  the  bottom  of  the  canyon  to  the  top,  may  be  either  a 


;o 


-!  i 


quartz  fissure  vein,  or  a  porphyry  dyke,  and  well  worth  ex- 
amining. There  are  manv  ways  of  studyinj^  rocks,  one  br 
hand  specimens,  findinj,^' out 'all  the  minerals  composinf^ 
them,  and  then  naming  the  rocks  from  which  they  came; 
another  bv  observing  the  appearance  of  large  masses  of 
u>c'  '•  M  the  field,  and  noting  their  mode  of  occurrence; 
an.i  la.Jy  if  we  wish  to  be  very  accurate,  making  thin 
microscopic  sections  and  a  chemical  analysis,  but  for  the 
average  prospector  these  last  will  lie  rarely  necessary. 

If  a  prospector  bought  a  manual  to  study  rocks,  for  prac- 
tical purposes,  he  would  find  himself  amongst  a  sea  of  names 
of  varieties  of  rocks,  nine-tenth  of  which  it  is  safe  to  say  he 
would  never  meet  with  in  his  field  experience. 

To  sa\'e  him  the  trouble  of  wading  through  such  books, 
we  select  just  abcnit  as  much  .is  a  p-rospector  is  liable  to 
meet  with  in  the  field  or  find  practically  useful,  saying  little 
also  about  such  common  rocks  as  ;ire  familiar  to  e\ery  one. 

Those  that  need  most  deliniti<jn  and  arc  of  most  impor- 
tance in  the  mining  field,  are  the  crystalline  rocks,  belonging 
to  the  class  called  metamorphic  and  igneous  ;  the  last  es- 
pecially needs  careful  determination. 

Nearly  all  sedimentary  rocks  (limestone  excepted)  are 
derived  from  fragments  (jf  igneous  and  metamorphic  rocks. 
Probably  nine-tenths  of  the  sedimentary  rocks  are  derived 
from  granite  alone,  the  remainder  fn^m  the  igneous  rocks, 
such  as  porphyry,  basalt,  etc.  By  describing  the  parent 
r<jck,  the  deri\ati\e  (jue  is  more  easily  made  out. 


ROCK    MAKINC.    MINI  RAI.S. 

Crystalline  rocks  are  made  up  of  certain  distinct  minerals, 
most  c)f  them  of  quartz,  feldspar  and  mica  with  sometimes 
also  hornblende  and  augite.  Other  minerals  may  hjcally 
occur  as  occasional  elements. 

Ol'AR'i'Z  scarcely  needs  description  being  so  well  known. 

The  hexagonal  prism  of  this  crystal  is  too  hard  to  be 
scratched  with  a  knife  and  will  scratch  glass.  This  dis- 
tinguishes it  from  calcspar  and  barite,  for  which  it  might  be 
mistaken  in  the  field,  moreover  it  will  not  efferxesce  with 
acids. 

Thk  Fki.dsi'AKS  are  nearly  as  hard  as  (piartz.  Their  colors 
are  white,  grevish  and  llesh-color.  They  are  rarely  as  trans- 
jKirent  as  (juartz,  being  generally  opaque.  Their  form  of 
crystallization  is  dilferent  from  quartz,  and  in  a  vein  they 
show  (jne  smooth   face  of  their  crystal,  whilst  the  rpiartz  is 


51 


more  like  crushed  loaf-sii/ji^ar.  In  a  pf^rphyry  the  feldspar 
crystals  are  very  distinct,  and  j^i\'e  a  characteristic  spotted 
appearance  to  the  rock.  Two  wirieties  of  feldspar  are  char- 
acteristic of  the  crystalline  rocks,  one  called  orthoclase  or 
common  feldspar,  a  potash-feldspar,  the  (jther  called  oligo- 
clase,  a  soda-lime-feldspar.  The  former  is  very  characteris- 
tic of  granitic  rocks  as  well  as  of  igneous  porphyries,  the 
latter  is  rather  more  characteristic  of  iiKjre  recently  erupted 
igneous  rocks,  such  as  diorite,  basalt,  andesite,  etc. 

Orthoclase  is  generally  in  large  crystals,  olig(Jclase  in 
small.  When  the  crystals  are  very  small,  it  may  take  a  mi- 
croscopic examination  to  determine  to  which  variety  of 
feldspars  they  may  belong.  The  oligoclase  and  plagioclase 
crystals  in  igneous  rocks  are  commonly  but  little  white  dots. 

T(^  determine  accurately,  microscopic  slides  and  chemical 
tests  must  be  made,  but  this  is  scarceh'  within  the  scope  of 
the  prospector  wIkj  wants  to  guess  roughly  at  sight  as  to 
the  name  and  character  of  a  rock. 

Mica,  both  black  and  white,  needs  no  description. 

HoRXHLKNDF,  differs  from  mica  in  being  oi  a  duller  lustre 
and  (jf  a  different  form  of  crystallization  as  shown  in  the 
plate.  The  color  is  a  greenish-black;  the  greenish  tint  is 
distinct,  when  the  crystal  is  struck  by  a  hammer. 

AluniK  or  Pvroxknk  is  scarcely  distinguishable  from 
hornblende.  In  Colorado,  augite  is  mainly  confined  to  two 
kinds  of  rock,  basalt  or  dolerite  and  andesite,  both  of  compara- 
tively recent  volcanic  origin.  Hornblende  and  niica  are 
common  to  nearly  all  the  metamorphic  and  igneous  rocks. 

Tai.C  amongst  miners  means  almost  an\'  soft,  sticky,  or 
slipper3^  decomposed  rock,  but  strictly,  talc  is  ^  pale 
green,  soft  mineral  like  mica  and  is  a  silicate  of  magnesia. 
Steatite  or  soapstone  is  massive  talc.  Miners  often  wrongly 
call  any  soft  clay  or  rock,  soapstone  also. 

Chlorite  is  another  magnesian  mineral,  of  a  gieen  and 
soft  character.  Chlorite  is  again  a  name  given  h>  almost 
any  greenish  rock  of  a  schistose  and  soft  decomposed  char- 
acter. 

Cai.ci  TK  is  carbonate  of  lime  crystal,  the  element  of  lime- 
stone, and  is  distinguished  by  softness  and  effervescing  in 
acids. 

DoLOMi  rE  or  carbonate  of  lime  and  magnesia  is  very  like 
calcite  and  is  the  element  of  dolomitic  or  magnesian  lime- 
stone. Doh^mite  effervesces  with  much  greater  difBculty 
than  true  limestone.  To  effervesce,  the  dolomite  should  be 
powdered,  and  the  acid  heated. 


( f 


52 

fivi'SliM  01  sulphate  of  liiiK-  can  Ix:  Histiii^niishcd  l>v  its 
i-xtrcine   softness,  hcinj,'  scratched    hy   the    lin^u;r  nai   ;    it 

riocs  not  cHijrvesce    hue   Mnic. 

HAKiiKor  "heavy  s[)ar"  oc- 
curs in  some  veins,  hut  not  as 
a  constilnent  of  rocks.  it 
i()(>l<s  lil<(;  calcspar,  hut  is 
heavier  and  will  not  elfc-rvesce 
with  acids. 

I'l.i'oK-si'AK  otcasionally  oc- 
(  nrs  in  veins,  in  (  uhes  or  mas- 
sive It  is  easily  scratcherl 
with  a  knife ;  its  colors  ar«,' 
/riccM,  purple;,  yellow,  hint;  or 
while. 

(iAk.\;  IS,  (iKii.N  Ki'iitDi  I  . 
Hl.ACK  'lori<MAl,l.NK,and  other 
minerals  or  ^ems  may  occ  ur, 
hut  not  as  important  consti- 
tuents of  the  rocks. 

I  K\'SI  AI.I.I.M.    .\li;i  A.MOKI'llUJ 
l<()(•KS. 

(iKANl'l  1;.—  Hej.;inninjj;^  with 
the  ji;ranitic  series  of  the 
Arcluran  u^r.,  j.(ranite  proper 
is  massive,  shapeless,  or  amor- 
phous anfl  shows  no  heddinj.( 
planes  or  other  sijj^ns  of  lormer 
.^tratilication.  It  is  thorou/^hly 
crystalline  like  liimp-sujj^ar. 
Hv  some  it  is  consid(;red  a  t  rue; 
igneous  rock,  one  that  has  heen  thoroughly  fused  hy  heat, 
as  nuich  as  the  lavas  or  molten  iron  ;  hy  others  its  crystalline 
amorphous  conrhtion  is  supposed  to  he  the  result  of  extreme 
metamorphism  of  originally  sedimentary  he-dded  rocks,  such 
as  gneiss  or  schist,  the  two  latter  heing  sometimes  traced 
down  through  a  gradual  change  into  granitt'.  The  composi- 
tion of  granite  is  mica,  (|uart/.  and  feldspar  with  sometimes 
a  little  hornhlende.  The  micas  may  1)0  white  mica  (inus- 
covite),  or  hlack  mica  (hiotite).  Both  orthoclasi;  and  oligo- 
clase  feldsjiar  mav  he  pn.'sent,  hut  more  commonly  the 
former,  which  is  often  a  pinkish  llesh  color,  (iranite,  in  its 
crvstalline  texture,  differs  hoth  in  character  aiifl  appearance 


I'l.Ari;  XVlll. 

I.  'lifii  liiiii  Oli({()(lasc  I'cldsp.ir.  2. 
MoiKii'Iinii  ( )rth(>('l:isc  l''«;l(t^l);^r.  3. 
Carlsbad  Twins  Kf-Mspar.  4.  Aii^ilc 
iir  I'yniXL-iie,  5  and  6  llciriiMeiidc. 


53 

from  porpliyries  aiifl  other  if^neous  njcks,  in  the  fact  tli.'it 
its  crystals  arc  all  jumhicfi  up  and  cnishcd  toj^cthcr  like 
loaf-sugar,  and  none  of  the  crystals  are  s<:t  like  plums 
in  a  [jiuldinj^,  fiistinctly  in  a  haf;kinj.f  or  paste  of  very  small 
(  rystals  of  amorjihous  or  j^lissy  mat(;rial,  as  in  th<;  [jor- 
phyries  or  ij^neous  rorks.  (^ranitt;  is  probably  tli-  olrjest 
and  deepest  rock  known,  it  is  often  fraversed  by  sparry 
veins,  b<jth  j^reat  and  small,  which  consists  of  i\n:ir\y.  <;r 
fc-Mspar  or  both,  in  a  mort;  sj^arry  condition  than  when 
diffused  through  the  parent  rocK. 

These  so-called  "fjuarl/  veins  "are  <^»ften  callerl  "granu- 
lite  "  or  "  i)egmaiite  "  (yr  "graphir;  granite-."  The  rpjart/  and 
feldspar   are   olten    arranged    in    [)arallel   jjlates,  giving  on 


Granite 
I'l.AlK    XIX. 


Pf  8M/»T(TC 

Pl.AlK      XX. 


I'l.ATK     XXI. 


cross-section  curious  marks  like;  Hebrew  characters,  hence 
the  word  graphic.  The  bulk  of  fjiir  so-called  fjuart/  fissurci 
\eins  in  the  granite  mo.ititains  niay  be  cali(-d  [jegmatitic 
veins.  The  colors  of  granite  vary  fr'HTi  rerldish  to  gray,  or 
nearly  white  to  black,  acf;orfling  to  the  preponderance  and 
colors  of  the  micas  and  feldspars  in  them. 

Sykni'JK  is   little  more  ^ 

l^^gg^l    than     granit<;    in     which 
l'r/'^SJ^:rr*F,     horidjIend<;  supplies   tin- 
place  of  mica. 

(i.N'Klss  may  be  calli^i 
"beddc-d  granite,"  show- 
ing a  bt;dded  api>earance. 
(jneiss  is  (jften  curiouslv 

i-m.atkxxii.  =*'"'  pr'jtt'iy  i^'i"''*;''  :'' 

streaked  by  seams  of  mica 
dove-tailing  into  each  other.      If   mica   preponderates,    it   is 
called   "mica  gneiss,"  if  hornblerule  "  hornblenrlic  gneiss." 

ScHlS'i'  :-.,.iy  be  "ailed  himinatefi  gneiss  or  granite,  being  fin- 
ally di^iflerl  into  htn.ina  or  leaves.  This  foliated  structure  is 
rinetothe  arrangei;u,'nt  oi  the  flat-lying  crystals  of  -nica  or 


GnCI  5  I 


CoHTO/^TeoMicn  Schist 
Pi. A  IK  XXI 11. 


m- 


!  .? 


N  !i 


III 


hornblende  largely  composing  it.  It  may  be  a  mica-scliist 
or  a  hornblende  ..chist. 

Slatk  is  shale  altered  by  heat  into  a  hard  crystalline 
structure. 

OUARTZITE  was  originally  a  sandstontiC()mj)osed  of  quartz 
grains,  which  by  heat  have  been  partially  fused  together 
at  the  edges,  resembling  granules  of  tapioca  in  a  tapioca 
pudding.  Ouartzite  dififers  from  quartz  in  being  a  rock 
made  out  oT  pieces  of  (juartz,  and  not  the  original  mineral 
itself.  (Juartzite  may  be  white  like  sugar,  grey,  brown,  or 
rusty.     It  shows  a  true  stratified  structure. 

Marhi.k  is  limestone  similarly  changed  to  a  more  crystal- 
line condition. 

Serpf.ntine  is  a  arreen  magnesian  rock,  sometimes  ffjund 
with  marble  and  igneous  rocks  and  is  formed  by  alteration 
of  certain  minerals  in  the  latter. 

CRYSTALLINE    IGNEOUS    OR    ERUPTIVE   ROCK.S. 

These  are  rocks  which  are  supposed  to  have  been 
thoroughly  fused  or  melted  in  the  bowels  of  the  earth. 
Some  reach  the  surface  by  fissures  or  volcanic  vents,  others 
have  nevet  attained  to  the  surface  or  overflown  it.  but 
have  intruded  themselves  between  the  weak  places  in  the 
underlying  strata,  or  have  collected  and  cooled  deep  down 
below  the  surface  in  great  molten  reservoirs  called  "  lac- 
colites"  or  lakes  of  stone.  When  these  have  been  subse- 
quently uncovered  by  erosion,  they  may  present  the  forms 
of  considerable  mountain  masses,  like  the  Elk  Mountains, 
and  Henry  Mountains  and  Spanish  Peaks.  Geologists 
distinguish  those  rocks  which  have  pcjured  out  on  the 
surface  from  craters  and  volcanic  vents  as  volcanic  rocks, 
whilst  those  cooling  below  are  called  Plutonic. 

INTRUSIVE    PLUTONIC   ROCKS. 

The  component  minerals  of  these  intrusive  Plutonic  rocks, 
such  as  are  commonly  called  porphyrin's,  are  principally 
quartz  and  feldspar,  with  mica  or  liornblende.  In  color  these 
rocks  are  some  shade  of  grey,  green  or  maroon,  or  even  white, 
but  their  most  striking  characteristic  is  .i  general  spotted  ap- 
pearance. This  arises  from  more  or  less  large,  distinct,  perfect- 
ly formed  crystals  of  feldspar  or  quartz,  set  in  a  finer  grained 
crystalline  paste  or  background,  standing  out  distinctly 
from  it.  This  base  or  background  may  be  comparatively 
coarsely  crystalline,  hnely  crystalline,  or  so  finely  crystal- 
line, that  the  crystals  can  be  discovered  only  by  a  micro- 


55 


mrnmm 


W'v-i^ 


scope,  whilst  the  larger  crystals  seem  set  in  the  paste,  like 
plums  in  a  pudding.  In  the  depths  of  a  mine  the  por- 
phyry is  commonly  much  decomposed  by  water  action  or 
mineral  solutions,  and  even  passes  into  a  clay  or  gouge. 
The  characteristic  spotty  appe.irance.  from  the  presence  of 
individual  crystals  of  feldspar  may  even 
then  identify  the  rock,  or  by  chemical 
analysis  the  very  aluminous  character  of 
the  decomposed  rock  may  determine  its 
character.  When  feldspar  is  the  main 
constituent,  it  is  called  a  felsite  porphyry, 
when  a  certain  amount  of  quartz  is  present 
a  quartz  porphyry.  QunRTZiTEifMrNMOHmco) 

UiORi  IK,  whose  crystals  are  sometimes  pi^^TE  XXIV. 
porphyritic  in  character,  hence  called  por- 
l^hyritic  diorite  or  porphyrite,  belongs  also  to  this  intrusive 
or  l*lut<jnian  class,  difTering  only  from  the  others  in  the  fact 
that  its  feldspar  is  of  the  triclinic  plagio- 
clase  kind  rather  than  orthoclasc.  Morn- 
blende  is  a  prominent  constituent  of  this 
rock,  and  gives  it,  more  or  less,  its  dark, 
olive  green  tint.  In  appearance  it  re- 
sembles a  dark  syenite,  but  its  occurrence 
as  an  eruptive,  intrusive  rock  distinguishes 
it,  as  svenite  is  generally  a  metamorphic 
rock.  The  peaks  of  the  Elk  Mountains 
are,  matiy  of  them,  of  diorite.  Diorite  or 
porphyrite    is    the    so-called    porphyry    of 


PORPHYHITIcDlORITE 
IP0RPHYHIT£) 


Pl.ATF.      XXV 

Aspen,  above  the  ore  deposits. 


QUARTZ    PORPHYRIES. 

These  are  the  commonest,  and  may  be  said  to  be  the 
prevailing  eruptive  rocks  associated  with 
our  ore  di'posits  in  Colorado,  as  for  instance 
at  Leadville,  felsite  porphyries  as  well  as 
quartz  porphyries  occur  in  the  granite 
rocks  in  the  Central  and  Georgetown  min- 
ing districts.  All  these  rocks  are  common 
through  the  West,  and  (piartz  porphyries 
arc  the  most  common  eruptive  rocks  the 
prospector  is  likely  to  meet  with  in  his 
search  for  ore  deposits.  We  will  describe 
in  detail  one  or  two  typical  species,  though 
it  must  be  observed' that  these  porphyries  are  of  endless 
varieties  and  shades  of  appearance. 


Felsite  Porphyry 


Plate  XXVI. 


56 


I     I 


M'^-Uncoln  QuAnrz 

Pi.atkXXVII. 


OUARiz  Porphyry.— A  quartz  porphyry  is  a  porphyry 
that  contains  (juartz  crystals,  hirge  or  small,  in  addition 
usually  to  large  orthoclase  feldspar  crystals,  generally  of  a 
vitre(/us  glassy  variety  called  "  sanidin," 
together  with  small  crystals  of  hornblende 
or  mica.  As  a  typical  example  we  take 
that  which  forms  the  d\'ke  composing  the 

Eeak  of  Mt.  Lincoln,  Colorado,  called  Mt. 
incoln  (juartz  porphyry.     This  porphyry 

and    varieties   of   it   are   common    in   the 

western  mininj.^  sections  of  Colorado. 
In  appearance  it  is  a  gray  rock  spotted 

with  large  and  small  crystals  of  orthoclase 

sanidin    feldspar,  which    sometimes   show 

an   oblong   face   two   inches    long,  by  an 

inch  wide,  at  other  times  a  shape  like  the  gable  end  of  a 

house,  according  to  whichever  part  of  the  crystal  hapjiens 

to  be   exposed.     Sometimes  two  crystals  are    seeri    locked 

together,  f(M'ming  what  are  called 
Carlsbad  twins.  When  the  njck  is  de- 
composed, these  crystals  not  unfre- 
quently  drop  out  and  lie  as  pebbles  on 
the  ground.  With  these  may  be  als(3 
seen  rounded  ends  of  bluish  crystals 
like  broken  glass.  These  are  portions 
of  perfect  (piartz  crystals,  which  when 
extracted  show  a  six-sided  pyramid  at 
either  end.  These  larger  crystals  are 
set  in  a  crystalline  ground  mass  of 
much  smaller  crystals  of  the  same  kind, 

together  with  many  little  black  cubes  of  shining  mica,  or 

duller  lustred,  longer,  rectangular,  oblong  crystals  of  horn- 
blende.   This  porphyry  is  eruptive  and  intrusive,  occurring 

in  dykes,  intrusive  sheets  and  laccolites. 
Lkadvili.k    Whitf.    Porphyry. — 

At  Leadville  there   is   a  quartz   por- 

phyrv  known  as  the  Leadville  white 

porphyry  or  "  block  porphyry  "  by  the 

miners,  which  needs  description  as  it 

is  the  one  that  more  especiallv  is  asso- 

dated  with  the  rich  <jre  deposits.     It  »on.BUNocJ\mrz,M,o.. 

IS   a  white,    compact,    homogenetnis         M-toNcr/Tcff/iBNEr 

lofjking  rock,  not  unlike  a  shaly  white  Pl\  IF  XXIX 

sandstone   or  (|uartzite.     It   consists 

of  feldspar,   (juartz  and   a    little  mica.     Its    porphyritic   or 


iEAOVILLEWHireQU/^ftTZ 

,      Porphyry 

Plate    XXVIII. 


57 

spotted  character  is  so  iiulistinct  that  one  would  be  inchned 
to  call  it  a  felsite  at  sight  rather  than  a  true  porphyry,  but 
the  microscope  reveals  perfect  double  pyramids  of  quartz 
and  individual  crystals  of  feldspar  set  in  a  paste  of  the 
same  minerals.  It  is  often  stained  by  concentric  rings  of 
iron  oxide  and  marked  with  wonderful  imitations  oi  trees. 
The  latter  have  earned  for  it  the  title  of  "  photographic 
rock"  or  "dendritic  porphyry."  These  markings  are  only 
the  crystallization  forms  of  oxide  of  iron  or  manganese, 
something  like  fern-frost  on  a  window-  ne.  The  porphyry 
is  very  shaly,  and  breaks  up  in  thin  slabs;  hence  called  also 
"block  porphyry."  It  is  common  at  Leadville  and  is  also 
found  elsewhere.  In  the  same  region  there  are  many  other 
varieties  of  quartz  porphyry  such  as  the  "gray  porphyry," 
the  Sacramento,  and  the  pyritiferous  porphyry.  The  latter 
is  often  gold  bearing. 


YOUNGER   EFFUSIVK   VOICANIC   ROCKS. 

These  intrusive  plutonic  porphyries  and  diorites  are 
generally  older  than  the  other  class  which  reached  the  sur- 
face and  poured  over  it  and  which  may  be  called  for  distinc- 
tion "'effusive"  volcanic  rocks. 

Typical  of  these  we  may  cite  the  dark  basalts  and  dolerites 
that  often  cap  the  table  lands  of  the  prairie 
region  and  overlie  our  coal  beds.  A  pink- 
ish or  dove-col(^red  rhyolite  also  caps  some 
of  the  mesas  and  in  certain  districts  an 
andesite  lava. 

Doi.ERiTE  AND  Basalt. — The  latter  be- 
ing scarcely  more  than  a  line  grained 
variety  of  the  former,  are  very  dark  rocks, 
consisting  of  dark,  heavy  minerals,  such  as 
augite,  magnetite  and  a  plagioclase  feldspar 
called  labradorite.  Such  minerals  are  said 
to  be  basic,  and  the  rock  composing  then^ 
also  basic. 

Andesite  is  very  like  dolerite,  though  generally  a  lighter 
gray  or  pink.  Hoth  augite  and  hornblende  may  occur  in 
it,  niore  especially  hornblende,  sometimes  mica  also.  The 
feldspar  is  called  andesite  feldspar  from  the  Andes  Moun- 
tains. 

Rhyolite,  under  the  microscope,  shows  a  peculiar  flow- 
ing structure,  hence  its  name  from  "  rheo "  to  flow.  The 
lighter  rocks  in  Colorado  and  the  West  are  generally  rhyo- 


I'l.ATK  XXX. 


5« 


lites  rather  than  true  trachytes.  Their  ccjlors  are  |)ale  j,nay. 
white,  pink  or  sometimes  Hark. 

Khyohto  consists  of  a  fUient.  vitreous,  jriound  mass  or 
paste,  usuallv  containiiiff  crystals  of  sanidin  feldspar,  or 
even  of  (piartz.  When  these'crystals  are  conspicuous  so  as 
to  ^rive  the  rocks  a  porphyritic  appearance  it  is  called 
"  liparite." 

in  some  cases  it  may  have  even  a  j^ranite-like  appearance, 
the  crystals  of  ((uartz.  mica  and  feUlspar  beiri'r  more  or  less 
intermi.xed;  then  it  is  called  \evadite.  it  is  an  acidic  rock 
consisting  of  acifl  minerals  mainly. 

Trachvtf:.  from  "  trachus"  rough,  is  a  light  colored  rock, 
with  a  peculiar  characteristic  rough  feel,  due  to  niicroscoi)ic 
vesicularity.     It  consists  of  a  ground  nu^ss  of  sanidin  feld- 


I' 


Platk  XXXI. 


Pl.ATK   XXXII. 


spar  and  augite,  containing  crystals  oi  the  latter.  In  ninety- 
nine  cases  out  of  a  hundred  in  Colorado  at  least,  also  in  the 
West,  rocks  which  are  popularly  called  "  trachytes  "  are  rhy- 
olites  or  porphyries. 

Basai.I's  and  some  of  the  other  extrusive  volcanic  rocks 
assume  a  columnar  form  on  cooling.  .Also,  on  the  surface 
of  the  flow,  the  lava  becfjines  minutely  honey-ctiuibed  like 
sponge,  from  escape  of  steam.  This  is  called  scoria  and 
when  these  holes  are  tilled  with  almond-shaped  white  crys- 
tals, amygdaloid.  At  other  times  the  rock  is  a  rolcanic 
breccia  ;  that  is,  angular  blocks  of  lava,  great  or  small,  are 
cemented  together  by  lava.  This  probably  was  caused  when 
the  lava  was  pouring  out  of  the  fissure  slowly,  some  por- 
tions congealed  and  were  broken  up  by  the  onward  Ihjw, 
and  again  iinohed  in  the  molten  mass  without  being  re- 
melted.  Enormous  masses  of  volcanic  breccia  cover  the 
San  Juan  region.  Sometimes,  by  steam,  the  la\a  is  blown 
into  dust  and  descending  with  water,  is  worked  up  into  a 
volcanic  sandstone  known  as  volcanic  "tufa"  or  "  tufV.'" 

Ohsidian  is  vitntied  lava  or  volcanic  glass. 


II' 


59 


CHAPFER    V. 

T   .E   PR()SI»i:CT()R"S    MIN'KRALOGY. 

TJierc  are  t\\«»  classes  ol  iniiuMals  in\vl)i(li  llu-  prospector 
is  interested,  one  may  be  called  the  "earthy"'  minerals, 
such  as  cjnart/,  calcspar,  etc.,  associated  with  the  precious 
ores;  the  other,  the  metallic  minerals  constitutinji"^  the  ores 
themselves. 

Both  of  these  he  wants  to  know  at  sijrht,  or  to  determine 
with  the  simplest  appliances,  (ienerally  spcakinjj^,  his  cye- 
sijj^ht.  his  pocket-knife,  his  ore-jj^lass  and  a  little  acid,  will  he 
all  he  needs,  nor  need  he  concern  himself  about  a  j^ifat 
inimber  of  minerals,  if  he  only  knows  the  comniDiier  ones 
well.  Tiie  earthy  minerals  f(;rm  the  jj^anjj^ue  or  \einsl(jne  of 
the  vein  in  which  the  precious  ores  are  distributed. 


MART  MY    C.ANdrK    MINT.RAI.S, 

'i'hese  are  princ'|)ally  quartz,  calcite,  or  limespar,  dolo- 
mite, lluorspar  and  baryta,  all  of  wliich  we  have  alreafly  des- 
cribed amonjj;  rock-forminjj[  minerals.  These  crystals  are 
nearly  always  to  be  found  in  the  adjaci'nt  rock  as  elements 
of  that  rock,  and  their  more  sjiarry  coiulition  in  the  jj^anji^ue 
of  the  vein  is  deri\ed  by  solution  from  the  enclosing  country 
rock.  Thus,  a  \-ein  runninjjf  throufj^h  tfranite.  will  contain 
mainh"  quart/,  thoujj^h  calcite  and  fluorspar  may  be  asso- 
ciated with  it  in  small  quantities.  A  vein  passin^j  throuf.;^h 
limestone  naturally  carries  calcite  or  limes|)ar.  Sometimes 
baryta  is  associated  with  the  calcite.  especially  if  near  the 
limestone  ore  deposit  there  are  porphyries. 

Har\ta  has  been  detected  as  an  element  of  some  por- 
phyries which  are  probably  ore-bearinjj;^,  and  when  prospect- 
in*;,  we  ha\e  fouufl  baryta  to  be  jj^enerallv  an  indication  of 
ore  near  bv.  whilst  calcspar.  or  (piart/,  afone.  mayor  may 
ni)t  be  barren.  The  float,  or  loose  surface  indications  of 
ort'-deposus  at  Aspen  is  commonly  made  up  of  calcspar 
and  baryta. 

Ki.roRsi'Ak  in  Colorado  is  j^enerally  confined  to  \eins  in 
the  f^ranitic  rocks  ar.d  in  some  of  the  eruptive  rocks.  Its 
presence  is  a  j2^(jod  sif.i;^n  of  ore. 

OxiDF.s  OF  Iron  and  Manc.ank.sk. — These,  often  mixed 
tojj^ether.  form  a  lartje  element  in  the  j^anjj^ue  matter  */'  a 
\  ein  or  ore  deposit.     Manganese  can  be  recognized  by  its 


(o 


i 

I 


' 


)!  ! 


Platk  XXXIII. 

Spathic  Iron. 


<lark  black  color.  A  beautiful  rose-coloifd  carbonatc-of- 
luaj^Miifsc  called  Rnoixx  koshk  is  occasionally  met  with, 
associated  with  quartz  and  metal  in  some  veins. 

Cakiion.v  ir.-oi'-Coi'i'KR  is  of- 
ten associaterl  with  this  jj^anj^nie 
matter.  It  is  readily  distin- 
guished by  its  bright  >j;^reen  <jr 
azure  blue  color.  "  I''loat  "  is 
commonly  rusty  with  iron-oxide 
streaked  with  stains  of  copper- 
carbonate. 

Si'AiHic  Ikon  ok  Iro.n  (\\k- 
iioNATK  OK  SiDKRiri'.  occurs 
here  and  there  in  the  j^auf^ue  of 
fissure  veins.  It  is  very  like 
brown  feldspar  but  heavier. 
These  few  common  minerals 
cover  nearly  all  that  are  generally  met  with  as  indications 
of,  or  in  important  connection  with,  ore  dcfiosits. 

As  a  rule  most  of  these  minerals  occur  in  a  massive  state 
rather  than  as  indixidual  crystals  in  a  \ein. 

MF'.rAI.MFF.ROUS    MINKRAI.S. 

Through  these  gangues  of  various  characters,  the  pre- 
cious metals  are  distributed  in  long,  narrow  patches  ov 
strings,  or  in  large  crystalline  masses,  or  in  scattered 
cr\  stals,  or  in  decomposed  masses.  The  gangue  matter  is 
generally  in  the  majority  in  a  vein,  and  the  ore  thinly, 
sparingly,  and  irregularly,  distributed  in  it.  When  a  \'ein  is 
said  to  be  ten  or  more  feet  wide,  it  is  not  to  be  supposed, 
that  ten  feet  of  solid  ore  is  meant,  but  that  this  is  the 
width  of  the  gangue  betw'een  walls.  The  ore  body  may  be 
only  a  few  inches  wide.  The  streak  or  main  b(jdy  of  ore 
called  the  "  pay  streak  "  has  a  tendency  to  keep  near  one 
wall  or  the  other,  or  at  times  to  cross  from  wall  to  wall. 

IlIOH    AND    LOW   GRADE  ORKS. 

In  gold  veins,  flakes  or  wires  of  "  free  "  or  "  native  "  gold 
<jccur  in  the  dec(jmposed  gangue;  and  sometimes  in  the 
pure  undeconiposed  (juartz,  "native"  silver  is  found  in 
much  the  same  way,  but  more  as  specimens  than  as  con- 
tinuous bodies.  Isolated  patches  of  rare.oi  valuable  miner- 
als, such  as  Ruby  silver,  Horn  silver.  Silver  glance,  etc., 
occur  locally  in  parts  of  the  vein,  sometimes  coating  stalac- 


6 1 


titcs  or  crystals  of  a  "  viik:I>  "  or  cavity  lined  with  ([uartz  or 
otiitrr  crystals.    An  assay  from  sncli  picked 
s|)eciinens  would  fj;ive  a  very  uiitair  aver-         -^-^^^v    v^ 
aj.(e  of  a  mine  or  prospec* 

The  hulk  of  the   profits  of  a  mine  come 
from  the  coiiimoiier  minerals  such  as  j^al 

„:* I I   I i I   c ii. 


DECOMPOSED   MINKRAr.S. 

Sometimes  the  franjj^ue  matter  contains  a  \ariety  of  de- 
composecl  ore  in  rich  seconflary  coir- l)inaf ion  inti'nately 
mixed  through  its  mass  and  rarely  n.  ^ernible  hy  tho  eye. 
Thus  yellow  mufl  from  a  mine  mav  assa)  hijj[h.  from  the 
presence  of  inxisihie  chlorides  or  su1j)hurets  of  silver.  No 
accurate  estimate  of  the  \alue  of  a  mine,  or  even  of  a  piece 
of  ore,  can  he  found,  without  an  assay  or  mill-run.  The 
reason  for  such  richness  in  decomposed  surface  products, 
is,  that  nature  has  been  for  ajj^es  leachinjj^  out,  concentrating' 
and  C(jml)ining  in  richer  forms,  the  essence,  so  to  speak,  of 
the  \ein. 

Grav    CoiM'KR    (Tkirahrdritk).     Besides   the    ordinary 

f^alena  and  pyrites  common  in  most 
mines,  we  sijinetimes  lind  con- 
siderable bodies  of  ^ray  copper  in 
mines,  or  intermingled  with  other 
ores.  This  is  generally  a  rich  silver- 
bearing  ore,  running  from  60  ounces 
to  some  thousands  per  ton.  It  gen- 
erally occurs  massive,  rarely  show- 
ing its  pyramidal  "  tetrahedrite  " 
crystals.  In  appearance  it  is  not 
Pi  A TK  XXXV  unlike    a    fieshly    broken    piece  of 

'    ,.,       I    ,'.    ,     bronze.     It  is  more  common  in  fis- 

Oray    Copper   Uertrahednte.)      ^^^^^    ^^^.^^    .^^   ^^,^^.^^    and    CruptiVC 

rocks  than  in  limestone.    In  Halls  VaUev.  Colorado,  it  is  asso- 


I  :i^l 


■Mflu^ail 


riia^ 


62 


t 


oiatcd  with  baryta  in  a  vein  in  the  gneiss.  It  occurs  in  the 
(icorgetown  veins  in  granite.  In  the  San  juan  district  it  oc- 
curs also  associated  with  baryta  in  the  Bonanza  mine  ;  and 
an  ore  not  identical  with  it  in'coniposition.  but  very  like  it  in 
appearance,  called  bisniuthinite,  consisting  of  bismuth,  anti- 
mony, copper  aad  silver,  is  characterisfc  of  that  region  and 
is  rich  in  siKer.  lUsmuthinitc  has  a  more  shiny  tin-like 
appearance  than  gray  copper,  and  the  red  color  which 
bismuth  gives  to  charcoal  under  the  blowpipe  readily  dis- 
tinguishes it  from  gray  copper, 

I.OCAI.    VARIA  I  HiNS    IN    VAMK    OK   ORES. 

There  are  locally  in  dilTerent  mining  districts  considerable 
differences  ii.  the  \alue  of  (ertain  minerals  and  ores.  In 
one  district  gray  copper  may  rarely  exceed  60  ounces  ot 
sil\-er,  in  another  it  is  invariably  o\er  100  ounces. 

A  coarse  galena  is  generally  ]V)or  in  siKer,  while  fine 
grained  "  steel  galena"  is  generally  rich  in  siKer,  but  the 
reverse  may  also  be  the  case.  \\\  some  (jf  the  mines  at 
Aspen,  fine  graineri  galena,  especially  near  the  surface,  is 
quite  poor  in  siher,  while  in  other  mines  in  the  same  dis- 
trict it  is  exceedingly  rich.  Localities  occur  also  where 
coarse-grained  galena  runs  well  in  silver  and  is  richer  than 
fine-grained  galena.  This  is  the  case  at  the  Colonel  Sellers 
mine  at  Lead\ille.  So  one  mining  district  or  even  one  mine 
is  not  a  rule  for  another. 

PvRiiE.s. —  Iron  pyrites  and  copper  pyrites,  common  in 
most  of  our  quart/  veins  in  granite  and  in  the  eruptix'e 
rocks,  mav  y!eld  both  gold  ami  siKcr,  but  usually  tlx? 
former.  There  are  certain  districts  more  characterized  by 
pyrites  than  others,  such  as  the  Central  City  district.  These 
are  gener.;liv  gold-jiroducing  districts.  Some  of  the  mines 
at  Hreckenridge  and  South  Park  have  strong  pyritiferous 
veins  in  erupti\e  dykes,  such  as  the  Jumbo  mine.  These 
have  of  late  produced  a  great  deal  of  gold.  The  sanu' dis- 
trict, however,  jiroduces  large  argentiferous  lead  veins. 
Pyrites  generally  fa\'or  the  granite,  eruptive  and  crystallized 
rocks.  The  cpiartzites  of  the  Lower  Silurian  of  South  Park 
and  Ked  (^liff  are  often  |iyritiferous  and  generally  gold-bear- 
ing. In  limesti.ne  the  pyrites  is  rare  or  absent,  its  place 
being  tilled  by  some  form  of  iron  o.xide.  In  the  deeper 
mines  of  Lead\ilie.  however,  this  iron  oxide  is  beginning  to 
pass  down  into  the  iron  sulphide  or  |)yrite  from  which  it  was 
derived,     Iron   pyrites  can  generally  be  distinp'.ished  from 


«apn 


' 


63 

copper  pyiitL's  by  its  paler,  more  brassy  color,  by  its  superior 
hardness  and  by  its  crystallizin<i^  in  cubes,  (^)pper  pyrites 
is  much  yellower  and  softer,  and  crystallizes  li^  a  more 
pyramidal  torm.  A  vein  may  flitter  with  showy  pyiites  and 
yet  l)e  cpiite  \'alueless.  It  usually  yields  more  gold  in  its 
decomj)osed,  oxidized  condition  than  in  its  unaltered  Litate. 
In  the  one  case  the  gold  is  free-milling,  and  in  the  other  it 
must  be  smelted  at  much  greater  expense. 

Sri.i'Hi  KKis. — This  term  amongst  miners  is  lo<jsely  used, 
and  often  means  some  decomp(Jsed  ore  whose  ingredients 
cannot  be  determined  at  sight,  l)ut  which  somehow  assays 
liigh  in  siKer.  True  sulphuret  or  sulphide  of  silver  is  a 
name  embracing  a  large  family  of  rich  silver  ores,  among 
which  are  '^tel)llanite  or  brittle  siher.  argentite  or  siher 
glance,  syhanite  or  graphic  tellurium,  and  polybasite. 

All  these  rich  ores  are  compounds  of  sulphur  and  silver 
and  other  ingrerlients  in  x'arying  jiroportions.  They  are 
somewhat  alike  in  appearance  and  not  always  so  easy  to  dis- 
tinguish. 

Akcikn  11  IK,  sih-er  glance,  or  sulphuret  of  silver,  is  of  a 
blackish,  lead-grav  color,  easily  cut  with  a  knife,  and  con- 
sists of  an  aggregate  of  minute  crystals.  Its  composition  in 
loo  parts,  is  sulphur  12.9,  siher  87.1.  Tuder  the  blow-pipe 
it  gives  olT  an  orlor  of  suljihur,  and  yields  a  globule  of  sil\er. 

Si  F.IMIANI  11;.  or  "brittle"  or  "black"  silver,  is  closely 
allied  to  argentite.  Its  com|)osition  is 
sulphur,  antimony  and  siher,  silver  being 
6(S.5  per  cent.  The  crystals  are  small. 
I'nder  the  blow-pipe  it  gives  off  garlic 
fumes  of  antimony  and  yields  a  dark 
globule  from  which,  by  adding  soda,  we 
get  pure  silver. 

Poi.viiAsri  K,  Common  at  (Georgetown 
and  in  some  of  the  Aspen  mines,  such  as 
the  Regent  or  j.  (".  Johnson,  on  Smuggler 
Hill,  is  like  the  others,  but  of  a  more 
flakv,  seal)'  and  graphitic  a|)pearance.  It 
is  not  unlike  very  fine-grained  galena, 
yielding  150  to  400  ounces  of  silver  per 
ton. 

These  sulphurets  sometimes  line  little  cavities  in  lime- 
stones with  a  dark  sooty  substance,  which  under  the  micro- 
scope pro\es  to  be  crystals  of  one  of  the  sulphurets  of 
silver.  Sometimes  also  a  rock  is  stained  all  through  a 
blackish  gray  by  these  sulphurets.     Iron  or  manganese  may 


Pi. A  IF.  XXXVI. 

Stcphaiiite, 


64 


produce  much  the  same  effect,  but  an  assay  will  soon  reveaF 
the  difference  Associated  with  such  a  rock  we  may  see 
flakes  or  wires  of  native  silver  that  have  emerged  from  the 
sulphide  state. 

CHLORIDES. 

CHf-ORiDE  OF  Silver  ("Horn  silver.''  or  Cerargyrite). — 
This  is  another  result  of  secondary  wcc<j:Mposition   from  a 
sulphide  state  (silver  sulphide).    It  is  a  green'sh  or  yellowish 
mineral,  like  wax,  and  easily  cut  with  a  knito.     It  is  a  very 
rich  ore  running  75.3  per  cent,  silver,  the  rei.>ainder  being 
chlorine.     As  a  seccjiidary  product  of  decomposition    it  is 
generally  found   near  the  surface  or  in  cavities,  sometimes 
deposited   on   calcite  or  other  crystals.     In   the  mines  at 
Leadville  it  is  commonly  associated  with  other  decomposed 
ores,  such  as  carbonates.     In  the  Chrysolite  mine,  a  mass 
weighing   several    hundred   pounds  was  found.      Chloride, 
bromide  and  iodide  of  silver  are  closely  related,  being  com- 
pounds of  chl(jrine,  bromine,  iodine  and  silver.     It  is  notice- 
able that  these  salts  are  the  elements  of  sea  water,  and  that 
these  ores  are  often  found  in  marine  limestones.     Accord- 
ing to  Mr.  Emmons,  the  change  at  Leadville  from  sulphifle 
to  chloride  was  produced  by  surface  waters;    these  waters 
are  found  to  contain  chlorine,  which  they  probablv  derived 
from  passing  through  the  dolomitic  limestones  wiiich  con- 
tain chhirine  in  their  crystals,  and  these  limestones  perhaps 
originally  deri\ed  it  from  the  sea  water  in  which  they  wt-re 
deposited.     Chloride  of  siK-er  is  found  at  Aspen  aiv!  abunrl- 
antly  in  the  outcrop  of  mines  in  New  and  Old  Mexico. 

.SULPHARSENITES. 

Rrnv  Silvf:k  (Pynirgyrite  and  Proustite).  Composed  of 
sulphur  17.7,  antimony '22.5,  silver  59.8=100.  Crystallizes 
in  rhombohedrons.  is  seen  in  spots  or  crystals  on  ;i  mass  of 
ore  of  a  deep  red  or  blackish  tint.  When  scratched  with  a 
knite  it  shows  a  bright  or  deep  red  color.  In  some  mines 
this  very  rich  ore  occurs  only  as  specimens,  but  in  others  it 
is  present  in  sufficient  (juantity  to  largely  influence  the 
value  of  the  ore  in  bulk.  In  parts  of  the  (iianite  .Mountain 
Mine  in  Montana,  it  constitutes  the  principal  ore,  associated, 
however,  with  other  mineral.  It  there  occurs  in  large 
masses  and  accounts  for  the  extraordinary  richness  of  th;it 
celebrated  n)ine.  Pnnistite  is  much  the  same,  only  lighter 
red,  and  consists  of  sulphur  19,4,  arsenic  15.1.  silver 
65.5  =  100. 


65 


CARBONATES. 

This  term  also  embraces  a  large  family,  the  commonest 
being  carbonate  of  leau  (cerussite)  and  carbonate  of  copper, 
(malachite  and  azurite). 

CoppKR  CARBONATE  Can  never  be  mistaken,  owing  to  its 
brilliant  green  and  azure  blue  color.  Copper  stains  are 
among  the  common  surface  signs  of  a  "  lead. '  It  is  gener- 
ally associated  also  with  rusty  stains.  Both  are  the  surface 
products  from  copper  and  iron  pyrites  forming  a  vein  below 
ground  which  may  or  may  not  be  profitable.  Copper  stains 
are  common  enough  in  many  rocks,  but  do  not  always  lead 
to  bodies  of  ore.  In  South  F^ark  the  red  Triassic  sandstones 
are  s<j  stained,  but  vield  no  ore.  Along  our  foothills  there 
is  quite  a  stained  belt  from  Golden  to  Morrison  and  through 
Bergen  Park.  But  few  promising  deposits  of  copper  or 
other  ores  have  been  found,  although  handsome  specimens 
of  native  copper  have  been  discovered  near  Golden. 

At  the  Malachite  Mine  on  Bear  Creek,  near  Morrison,  a 
prospect  was  at  one  time  opened  showing  a  good  deal  oi 
silicate  of  copper  (chrysocolla)  and  malachite,  but  for  some 
reason  it  has  not  been  worked  since. 

Coi'i'ER  in  its  native  or  uncombined  state  is  rare  in 
Colorado,  and  so  far,  we  have  as  yet  no  true  profitable  mine. 
A  great  deal  of  copper  is  found  associated  with  other  ores, 
and  is  extracted  by  some  of  the  smelters.  Carbonate  of 
Copper  is  commonest  in  the  limestone  districts,  as  might  be 
e.xpected  from  the  carbonating  influence  of  limestone  upon 
minerals  in  it,  or  mineral  solutions  passing  through  it. 
Carbonate  of  iron  (spathic  iron,  or  siderite),  constitutes  part 
of  the  gangue  matter  in  some  of  our  veins,  and  may  also  be 
found  associated  with  coal  seams  generally,  in  the  latter 
case  in  an  o.xidized  condition. 

Ckrl'ssite  (Carbonate  of  lead).  This  is  mostly  found  in 
the  limestone  districts  such  as  Leadville.  It  is  there  known 
in  two  forms,  one  called  "  hard  carbonates,"  the  other"  soft  " 
or  "  sand  carbonates."  The  crystals  of  this  ore  are  small 
prisms,  sometimes  combined  into  a  cross  shape,  of  a  pale 
grayish  white,  and  might  be  taken  for  some  form  of  car- 
b(Miate  of  lime  or  gypsum,  their  weight,  however,  soon  shows 
the  difference.  They  are  a  secondary  product  of  decompo 
sition  consisting  of  carbon  dioxide  and  lead  oxide  ;  as  a 
carbonate  they  effervesce  in  nitric  acid,  and  yield  lead  when 
heated.  Cerussite  is  exceedingly  rich  in  lead,  carrying  75 
per  cent.  The  white  lead  of  commerce  has  the  same  com- 
positi(jn.     In    Leadville    and   elsewhere   in   Colorado   it   is 


I 


Tnr-itinMrn'iTia 


66 


1      H 


tsilvcr-boarin.";  also,  and  thouf^h  low  in  silvLT,  the  facility  of 
its  treatment  at  the  smelter  makes  it  a  very  desirable  ore. 
As  a  rule  it  contains  less  silver  than  the  unaltered  ^^ilena, 
but  is  more  easily  treated  than  the  latter.  The  process  of 
chanjj^e  or  derivation  from  a  sulphide  state  (/.  f..  from  j^alena) 
Xo  a  carbonate,  is  well  shown  sometimes  in  a  piece  of  Lead- 
ville  ore.  A  central  cube  oi  j^alena  is  surrounded  by  a  grayish 
^reen  rinj^  of  sulphide  of  lead  oi  anglesite.  and  (Uitside  this 


Pi,ATK   XXX VII. 

Simple  and  Compound  Ciystals  of  Carbonate  of  Lead  (Ccrussite.) 

iiiay  as'ain  occur  crystals  of  lead  carboiuite.  Thus  the  pro- 
-cess  is  from  a  sulphide  to  a  suli)hate,  then  to  a  carbonate. 
'The  so-called  "hard  c;'.rbf)nates  "  is  a  brown  mass  consistini^ 
of  a  hard  flinty  combination  of  iron  oxide  and  silica,  imj)rejj^- 
nated  with  crystals  of  lead  carbonate,  with  which  are  often 
■silver  chlorides,  also.  Tlie"sand  carbonates"  result  from 
the  decomposition  and  breaking-  uj)  of  the  hard  carbonates, 
•or  from  a  mass  of  pure  crystals  of  carbonate  of  lead,  which 
iire,  by  nature,  loose  and  incoherent.  The  Leadville  mines 
.are  getting  below  these  products  of  decomposition  and 
entering  upon  the  original  sulphides  of  galena  aiifl  iron. 
The  yield,  however,  is  saifl  to  be  eipially  good. 

zi.vc-HLKNDK  (si'MALKRiTK),  "  15I,.\ck'j  .AC  K."  Common  in 
most  mines  ini.xed  with  other  ores.  As  it  is  a  \'erv  refractory 
jnineral  in  smel'ing,  much  of  it  is  not  desirable  in  a  mine. 
It  is  ep.oiiy  recogiiized  by  its  brown  resinous  look,  or  when 
A'-ery  black  by  its  pearly  luster.  At 
•Geoirgetown,  near  tlie  surface,  brown 
"' rosin-zinc-blende  "  carries  silver,  and 
is  associated  with  rich  ores,  such  as  poly- 
basite  and  gray  copper.  With  depth  the 
zinc-blende  becomes  more  abundant  and 
blacker,  and  loses  much  of  its  sih-cr 
proj)erties.  Zinc-blende  may  run  from  1*1. .\  IK  XXX\'I1I, 
ing,  to   twenty    dollars  '  siU-er,   and 


proi)e 
iiiotnii 
a'arely  as  high  as  $icxd  per  ton. 

In  sonic  mines  in  the  San  Juan  it  occurs  abundantly  near 


Zinc  Siilpliide 
(Zinc  Ulciidc.) 


HPPMHtp 


67 

the  surface  and  fades  out  with  depth.  We  have  no  true- 
xinc  mines  in  Colorado,  the  zinc  bein^  mixed  with  other 
ores.  In  some  mines  in  Pitkin  County  the  zinc  predomi- 
nates over  all  other  ores,  and  thouf^h  it  runs  hif^h  in  silver 
tiie  smelters  do  not  care  to  take  it,  on  acccnmt  of  its  refrac- 
tory character.  In  the  Eastern  States  where  zinc  smelting  is 
a  specialty,  such  ore  mij^ht  be  separated  and  both  silver  and^ 
zii-;  saved.     In  Missouri  zinc  and  lead  are  found  tof?ether. 

In  Colorado  there  are  no  mines  of  one  mineral  ah^ne,  as; 
in  some  other  parts  of  the  world.  We  have  no  true  lead^ 
zinc  or  copper  mines  ;  these  baser  metals  are  either  arp^entif- 
erous  or  auriferous,  and  their  baser  qualities  are  sacriticedl 
for  their  richer  ones. 


CHAPTER   VI, 


ORE    DEPOSITS. 


THKORIKS    REOARDIX(i   THK   ORIGIN   OF   ORK    DEPOSITS. 

A  prospector  will  find  both  a  practical  as  well  as  scientific 
interest  in  considering^  the  origin  of  ore  deposits.  Where 
fio  the  precious  metals  c<Mne  from?  What  is  their  origin  .^' 
How  are  mineral  veins  formed  and  how  do  precious  metals- 
get  into  them  ? 

The  remote  origin  of  metals  is  a  matter  of  speculation.. 
They  may  have  formed  part  of  that  gaseous  mist  from  which^ 
according  to  the  nebular  theory  our  planetary  system  was 
evoked.     As  this  passed  into  molten  condition  the  metallic 
vapors  may  ha\e   separated  into  various  combinations  and 
consolidated  and  been  arranged  in  the  general  make  up  of 
the  world  according  to  their  specilic  gravity.     Some  have- 
thought  that  the  interior  of  the  earth  may  be  more  metallif- 
erous than  the  surface  crust  since  the  earth  grows  heavier- 
toward  the  center.     Volcanic  rocks  coming  up  from  depths, 
unknown  contain  a  large  per  cent,  of  the  heavier  metals, 
particularlv  iron.     But  we  turn   from  these  speculations  to- 
theories  of  more  practical  interest  t(i  the  prospector. 

A  prevalent  theory  amongst  miners  and  prospectors  is- 
what  may  be  called  "the  igneous  theory  "  or  tlie  fiery  origirfc 
of  veins  anfl  metals.  They  are  apt  to  attribute  the  tissures. 
themselves  to  some  vi<dent  volcanic  outburst,  and  consider 


-fTrr'TT'Tnr"-''^^"^^*^' 


iill 


68 


^ 


the  quartz  gangue  or  veinstone,  together  with  the  metals,  as 
molten  volcanic  emanations  filling  at  onetime  a  wide  gaping 

fissure.  . ,     .        ,    ,    ,  , 

Others  demand  an  intense  heat  considering  that  the  metals 
in  the  veins  were  reduced  in  the  bowels  of  the  earth  by 
intense  heat  to  a  vaporous  condition,  which,  ascending 
through  the  fissures,  condensed  and  consolidated  in  a  crys- 
talline form  in  the  upper  and  cooler  porti(>ns  of  the  fissures, 
as  certain  sublimed  mineral  vapors  fn^n  a  smelting  furnace 
sometimes  collect  and  recrystallize  in  the  flues. 

By  many  prospectors  every  indication  or  surface  appear- 
ance of  a 'vein,  or  even  a  likely-looking  rock,  is  called  "a 
blow  out,"  a  term  suggestive,  at  least,  of  some  sort  of  vol- 


Platk  XXXIX. 

Fold  Passing  into  Fault  SHowing  Hrokcn  Characrcr  of  Fault  Fissure  and  Adjacent 
Rot-ks  Prodiicinjj  Later  a  Brecciated  Vein  and  "  Horses." 

canic  explosion  at  that  point.  With  them,  the  "  fire  and 
brimstone  "  origin  of  ore  deposits  ii>  as  deep  seated  as  the 
veins  in  the  rocks. 

These  ideas  contain  a  measure  of  truth,  and  were  naturally 
suggested  by  observing  that  our  ore  deposits  are  so  generally 
associated  with  volcanic  rocks  and  evidences  of  past  heat ; 
and  it  cannot  be  denied  bui  that  the  presence  of  these  vol- 
canic rocks  had  more  or  less  to  do  with  the  ore  deposits. 

The  modern  study  of  ore  deposits  inclines  to  the  belief 
that  we  need  not  draw  directly  upon  the  unknown  prof.)und 
supposed  ignited  regions  of  the  earth's  interi(jr  for  the  direct 
source  of  metals  found  in  the  veins,  nor  entirely  from  \'iolent 
explosive  volcanic  agencies,  nor  from  very  intense  heat,  but 


i.i« 


^^-^^^ 


69 


Platk  XL. 

A  Tight  Fault  Crevice  Being  Attacked  by 
Solutions  Producing  Finally  a  Narrow  Fis- 
sure Vein— Small  Dois  =  Ore  Solutions. 


rather  that  \vc  may  lotjk  nearer  home  lor  the  immediate 
source  of  both  metals  and  veinstone,  namely,  in  the  ele- 
ments of  the  common  country  rock  adjacent  to  the  ore 
deposits;  and  for  the  me- 
dium of  distribution  and 
concentration  o{  ore  and 
veinstone  from  nothing 
more  violent  or  volcanic 
than  water,  more  or  less 
heated  and  alkaline.  Nor 
is  it  so  absolutely  neces- 
sary to  suppose  that  the 
tilling  of  a  vein  fissure 
with  quart/  or  metal  must 
needs  come  up  from  pro- 
found depths,  and  from  a 
foreign  source;  but  (juite 
as  likely  from  the  adja- 
cent sides  of  the  fissure, 
or  even  from  abo\'e  the 
position  later  occupied  by 
ore. 

Veins  of  whatever  kind  are  not  vents  for  molten  volcanic 
matter,  but  simply  courses  for  water,  more  or  less  heated 
and  alkaline,  in  fact,  channels  lA  mineral  hot  springs  carry- 
ing earthy  minerals  and  metals  in  the  same  solution,  and 
dep<isiting  them,  partly  by  cooling  and  sometimes  by  chem- 
ical precipitation  and  mainly  by  relief  of  pressure  in  such 
openings  or  weal;  places,  as  may  be  found  convenient. 

The  origin  of  these  open- 
ings and  weak  places  in 
the  earth's  crust  is  various. 
The  class  of  great  fissures 
holding  "fissure  veins." 
cleaving  our  mountains 
from  top  to  bottom  to  an 
unknown  great  depth,  were 
caused  by  the  fracturing 
and  faulting  of  rocks,  in 
the  gradual  process  of  fold- 
ing upwards,  and  elevation 
of  the  mountain  system,  a 
process  so  slow  and  grad- 
ual that  it  may  be  even 
noticing  it.     The    relief   of 


Platf  XLI. 

Gash  Vein  Fissures  in  Jointed  Eruptive 
Sheet. 

progressing   now   without  one 


» htamtrntmrn 


70 


I 

I 


"I  t  li 
■'  '•■  I 
1  •' 


'•f^'ig  Plane 


Plate  XLII. 

Joints  and  Kedding  Planes. 


'vtreme   tension    from    folding  results  finally    in    faulting; 
hougn    the    fault    fissure 
;    V  extend  to  very  great 

dtj  ths  it  was  probablv  not 

vioicn*  but  gradual.    From 

time   to   time,     the    shock 

produced  by  the  grinding 

together  of  the  walls  of  a 

fissi-re  in  a  slip  or  jerk  of 

o:ilva  few  inches,  may  have 

given  rise  to  severe  earth- 

(juakes  ow  the  surface. 
A  great  fault  fissure,  too, 

was    likely   to   be   accom- 
panied by  minor  adjacent 

faults  and    als(j    by    small 

incipient  fissures  <)r  loose  fractures  of  the   rocks,  producing 

parallel  fissures  and  zones  of  fissure  veins.    Other  ojienings, 

occupied  now  by  fissure  \'eins, 
may  be  C(jm pared  to  those 
joints  common  to  all  rocks,  the 
re  suit  of  contraction  and 
shrinkage  of  the  granitic  or 
volcanic  rocks  from  a  soft, 
semi-plastic  condition  to  one 
more  solid  and  compact.  Fiut 
in  no  case  we  think  were  the 
fissures  now  occupied  by  veins 
50  to  100  feet  wide  originally 
wide  open  chasms  like  that 
which  swallowed  up  Korah. 
Dathan  and  Abiram  in  Bible 
history,  but  rather  cracks  fit- 
ting very  tightly   together   by  enormous  lateral   pressure 

such  as  we  sec  in  fault  cracks  of  the 

present  day  not  yet  occupied  by  vein- 
stone   or    gangue    t)r    metal    matter. 

These    narrow    cracks    were    worked 

upon  by  alkaline   and  acid    solutions 

and  enlarged  by  the  process,  the  rock 

gradually  eaten    into    being   replaced 

by  gangue  and  metal  matter,  a  process 

often  further  assisted  by  the  shattered 

character  of  the  rock  commonly  found 

adjacent  to  a  great  fault;  this  shattered  cavity  was  sooner 


Pl.ATK  XL  II  I. 
Jointed  Clranite. 


I>LATE   XLIV. 

Jointed  Slate. 


Pt'*-Au.w««Wrt  -  irwww^^w:^.-  •«iw«p«K)n!>tw«yt^iw>m)»^iif 


71 


or  later  eaten  out.  so  to  speak,  and  replarcfl  by  niiiu;ral 
matter.  Some  of  the  broken  rock  beinjj^  not  conaumeci 
in  this  way.  was  left,  forminjj^ 
fraj^^ments  in  the  \ein  which 
when  small  are  called  "  breccia  " 
and  when  larjije  "  horses."  The 
^reat  "  jj^ash  "  tissurt  such  as  we 
find  occupied  by  so  aV  '  lissure 
veins  in  volcanic  shoe  such  as 
those  of  the  Sa\  hi;.-  rejj^ion, 
Colorado,  appeal  '  >  L  '  due  not  so 
much  to  fj[reat  ear'*^  nio\'ements 
like  the  last,  as  toop..  niu^s  formed 
by  c<;olinj4^  and       nfaction  of  the 

lava,  somewhat ..    .1  ay  be  obser\'ed  .,    v|i,XTV 

on  the  cooliiif^  of  iron  in   a  slajj^ 

furnace.     Ore  deposits  of  lead  and         J"'"''' '"  Coiumn.ir  Hasalt. 
other  minerals  lorminjj;  bedded  deposits  in  limestones  find 
their  way  in   solution   throujj^h  the  vertical  joints  common 
to  all  water  formefl    rocks,  resuitinj^    fronj^  contraction  in 

consolidatinjj[  from  a 
soft,  muddy  condi- 
tion. Such  fissures 
are  short  but  they 
act  as  channels  to  a 
more  important  line 
of  weakness  occupi- 
ed bv  the  main  l)od\' 
of  the  blanket  ore 
deposits,  viz.:  the 
d  i  V  i  d  i  n^  line  be- 
tween one  stratum 
and  another.  An- 
other line  of  weak- 
ness for  the  attack  of  mineral  scdutions  is  at  the  juncture 
of  a  porphyry  sheet  or  dyke  with  some  other  rock.  The 
interval  between  them  is  often  occupied  by  a  "contact 
vein."  The  heat  of  the  \'olcanic  matter  tojj[Cther  with  steam 
may  have  influenced  the  solutions,  even  if  the  porphyry  did 
not  actually  supply  the  metallic  element  in  the  vein.' 


f'o/t/rtrf 


Platk  XLVI. 

Contact  Ore  Deposits  I{ct«.-ecn  Porphyry  .md 
l.imestcinf. 


n^I.DINd    AND    FAUI/nXCl. 


In  the  many  and  ^xc\\{  upheavals  of  the  earth's  crust,  re- 
sulting in  ccjutinents   risinj.^  abo\e   the   sea,  and  on  those 


Ill 

'!     ft* 


n 

continents  still  greater  and  sharper  upheavals  forming 
mountain  ranges,  rocks  have  been  much  broken  and  frac- 
tured, from  great  fractures,  forming  fissures  miles  in  length 
and  depth,  down  to  little  cracks  of  but  a  few  inches.  Much 
of  this  fracturing  has  been  caused  by  the  folding  and 
crumpling  upwards  of  strata  into  mountains,  accompanied 
bv  great  crushing  and  mashing  together  of  the  rocks. 
When  this  lateral  tangential  folding  and  compression  of  the 
rocks  reaches  its  maximum  intensity,  the  rocks  break,  and 
a  fault  or  slip  is  the  result,  with  its  attendant  fault-lissure. 
This  relieves  the  strain  for  a  while,  but  the  shock,  doubt- 
less at  the  time  accompanied  by  earth(|uakes  on  the  surface, 
resulted  in  a  general  breaking  up  of  the  arljacent  country 
into  many  parallel  and  smaller  faults  and  cross  faults,  be- 
sides a  general  shattering  of  the  ground  intermediate  to 
the  faults.  A  region  thus  faultefl  and  shattered  is  )ust  in 
the  desired  condition  for  forming  a  future  mineral  belt  <jr 
mining  region,  when  the  cracks  anfl  scars  thus  made  have 
been  healerl  and  tilled  up  by  mineral  matter,  brought  in 
through  the  agenc)  of  watery  solutions  more  or  less  alka- 
line or  heated. 

INTKL'SIVK    m;NF.(>IS    RoiKS. 

When  these  fault  fissures  descend  to  a  \-ery  great  depth, 
they  may  tap  the  molten  rock  reservoir  supposerl  to  lie  be- 
neath great  mountain  ranges,  and  the  molten  lava  or 
porphyry,  rushes  upward  through  the  weak  line  of  the  fis- 
sure, tills  it  with  its  matter,  wliich  on  cooling  becomes  a 
dyke  instead  of  a  mineral  vein.  These  eruptive  rocks  may 
(jr  mav  not  reach  (piite  to  the  surface  and  overflcnv  it  in  a 
lava  sheet.  H  they  do  not.  they  find  relief  by  intruding 
themselves  laterally  between  the  layers  of  stratified  rocks, 
whose  leaves  or  bedding  planes  may  have  been  partially 
opened,  like  the  leaves  of  a  crumpled  book  by  previous 
action  of  folding.  In  such  cases  the  por[)hyry  dyke  or  in- 
trusive sheet  may,  if  it  be  mineralized,  answer  all  intents 
and  purpose  of  a  mineral  vein,  or  the  ore  may  be  found  on 
one  or  both  sides  oi  such  a  sheet,  in  the  line  of  separation 
and  weakness  between  it  and  the  adjacent  strata,  or  it  may 
permeate  and  mineralize  by  a  "substitution"  process  an 
adjacent  porous  or  soluble  rock  such  as  limestone.  Thus 
both  in  the  dyke  or  intrusive  sheet  itself  as  well  as  at  its 
contact  with  other  rocks,  the  pn^spector  should  look  for 
signs  of  precious  metal. 

If  the  dyke  or  sheet  should  be  decompijsed,  clayey  and 


73 

rusty,  it  mav  contain  free  gold  disseminated  Ihnjugh  it, 
which,  at  a  depth  which  may  or  may  not  be  ever  reached 
by  mining,  passes  into  the  auriferous  iron-pyrites  from 
which  the  free  gold  originally  came.  In  this  case  the  ore 
will  be  no  longer  "free"  or  "free-milling."  but  of  a  charac- 
ter that  must  be  subjected  to  the  more  expensive  treat- 
ment of  roasting  or  smelting.  Little  stringers  «jr  veinlets 
of  quartz,  if  observed  in  sucli  an  eruptive  rock  should  be 
carefully  examined  ;•.:;  the  most  likely  source  of  the  richest 
gold  ore.  Som«;  of  our  most  noterl  gold  mines  in  the  West 
are  in  these  "rotten  "  mineralized  dykes  or  erut)ti\e  intru- 
sive sheets.  "Likely  signs"  in  such  would  lie  rusty 
"gossan  "  stains  of  green  carbonate  of  coj)per  and  gouge  or 
clav  matter.  It  is  W(jrth  observing  that  the  dyke  may  be 
only  valuable  as  a  mine  as  far  down  as  the  decomposition 
lasts  and  as  long  as  the  ore  continues  in  a  free  state.  Witli 
depth,  the  pyrites  of  the  undecomposed  lower  portion  of  the 
dyke  mav  be  found  too  poor  in  g<  'Id  to  pay  t(ir  smelting  e\en. 

As  this  desirable  state  of  decomposition  is  the  result 
niainlv  of  the  acti<jn  of  surface  waters,  a  prospector  may 
consifler  sometimes,  where,  on  the  outcron  of  such  a  flyke. 
the  rock  is  uKJst  likely  to  be  deepest  atiected  bv  surface 
action;  for  example,  more  probably  below  the  ofd  stream 
bed  than  on  the  t»jp  of  a  mountain,  but  this  is  not  always  the 
case.  Most  d\kes  and  intrusive  sheets  when  mineralized. 
are  mineralized  by  pyrites,  rather  than  by  galena,  hence 
they  are  generally  inon.'  gold-bearing  than  siKer-bearing. 
The  contact  deposits  adjacent  to  a  volcanic  rock,  may  ha\'e 
been  aided  in  their  deposition  by  steam  issuing  fn^m  the 
molten  mass,  or  by  heated  waters  or  steam  ascending  with 
it.  or  generally  by  the  heat  of  the  dyke,  as  heat  together 
with  moisture  is  a  great  solvent  of  rocks  and  promoter  of 
chemical  action. 

In  granitic  rocks,  if  a  "contact"  deposit  occurs  adjacent 
to  a  porphyry  dyke,  it  is  usually  a  (juartz  vein,  or  a  \ein 
composed  of  rpiartz  and  feldspar,  commonly  called  "peg- 
matite." Such  contact  lissure  veins  may  be  on  one  or  both 
sides  of  a  dyke.  The  Telluride  veins  of  Boulder  and  the 
gold  and  silver  veins  of  Idaho  Springs,  Central  and  George- 
town in  Colorado  are  often  so  situated. 

CONTACT   DEPOSITS. 


When  a  porphyry  sheet  intrudes  itself  into  limestone  as 
at  Leadville.  the  ore  may  be  looked  for  on  either  side  of  this 


74 

sheet;  but  more  commonly  below  it.  At  first  tlif  ore  seems 
to  ponncafc  tht'  liincstoru'  inmufliiitrly  ;it  tin.'  line  of  con- 
tact, but  •)  Mn  this  somewhat  horizontal  line,  it  is  a|it  to  run 
down  throuj,'h  joint  cracks  in  the  limestone,  enlar^'in^r  the 
cracks  bv  solution,  and  substituting.,'  or  replacinjj:  the  dis- 
solvcfl  ri)ck  with  silver-lead  ore,  by  a  process  called 
"  metasoinatic  substitution." 


t 


*1  V, 


Contact  Ore 


Ore  Bed 


Contact  Ore 


fJneina 


C 


^     Duke  $ 


Gneiss 


.5^ 

V 


As^ 


Platf.  XL VII. 


"  Contact  Blanket  "  Ore  Deposits  and  "  Contact  Fissure  Veins."' 

"  Metasomatic  "  means  literally  "an  interchaiijj^e  between 
one  body  and  .inother."  In  this  case  it  is  an  interchange 
between  metal  and  limestone,  by  which  the  limestone  is 
gradually   replaced,    m<jlecule   by   molecule,   with    metallic 


matter.  Tluis  we  may  suppose,  that  as  the  mineral  solutions 
were  workinj^  on  the  Mmestone.  rcjttinj^  and  soakhijj;  and 
dissolving  it,  as  eacli  molecule  of  lime  was  disscjKefl,  it  was 
replaced  or  suhstituted  hy  a  molecule  ol  metallic:  matter, 
until  a  lar)^e  body  ol  the  rock  was  replacerl  hy  ore.  This 
appears  to  he  the  true  way  in  which  most  ol  our  ore  hodies 
were  fornu'd  in  limestone  and  other  soluble  rock,  rather 
than  that  they  were  "washed  in  "  and  "deposited  "  in  "  pre- 
existinff  lar^e  cavities"  as  some  have  supp(jsed. 

HLANKKT    UKfOSITS  ON    MKDDINd    l'l,ANES. 

The  solutions  ha\inj^  worked  their  way  down  throujrii 
these  vertical  joints,  may  reach  a  second  line  of  weakness, 
viz.,  the  beddinjj[  plane  or  line  of  stratification  hiitween  one 
bed  or  stratum  of  rock  and  another,  anrl  deposit  alonj^j  it  as 
on  a  floor.  This  may  he  between  one  heavy  bed  of  linie- 
stone  and  another.  If  it  is  between  two  dissimilar  ro':ks, 
such  as  between  limest<jne  and  (juartzite,  or  even  between 
limestone  at)d  maj^nesian  limestonecalled  dolomite,  it  comes 
under  the  name  (;f  a  "  contact  "  fleposit.  Thus  it  is  iiilice- 
able  that  besides  ji^reat  fissures,  lines  of  weakness  or  "  bed- 
ding planes"  are  favorite  places  for  ore  deposits,  to  which 
the  natural  vertical  joints  often  act  as  feeders,  as  well  a^ 
themselves  containing  large  "pockets"  or  "chambers"  of 
ore.  When  the  deposits  are  confined  to  these  "  pockets  " 
and  there  appears  to  be  no  "  blanket  "  dejiosit,  the  mine  is 
said  to  be  "  pockety,"  and  after  a  "  pocket  "  is  exhausted  an 
immense  amount  of  money  and  work  and  blind  "  gophering  " 
(jften  follows  in  hunting  for  another  pocket.  There  is  in 
this  case  little  rule  to  guide  the  prospector.  Locally,  l)y 
experience  in  the  mine,  he  may  notice  that  some  tine  line  of 
gypsum,  calcspar,  or  iron  stain  is  apt  t(j  lead  t(ja  pocket  and 
f()llow  it.  In  the  mines  of  Aspen,  where  tb.e  mineral  zone 
lies  irregularly  but  generally  near  about  the  line  ivhere  the 
limestone  becomes  dolomised.  a  miner,  when  his  ore  "  plays 
out."  follows  as  closely  as  l.e  r^^\  this  line,  which  he  is  able 
to  do  by  the  dilTerc'U  hardness  of  the  limestone  and 
dolomite,  the  latter  vUising  his  pici.  to  "ring."  In  every 
mine  there  is  generally  some  local  si.ni  t(j  assist  the  miner 
in  following  up  his  lost  ore. 

SURFACE  SIGNS, 

The  prospector  in  hunting  o:;  the  surface  outcrop  for 
signs  of  sucli  contact  or  blanket  or  pocket  deposits  must 


1:1 


I' 


76 

look  out  for  sipns  of  flccomposition  alonj?  the  line  of  con- 
tact, such  as  lead  carbonates,  carbonate  of  copper,  oxide  of 
iron,  together  with  crystalline  matJer  such  as  calcspar, 
gypsum,  or  barvta.  He  may  also  observe  in  the  vertical 
j()ints  leading  down  from  the  surface  into  the  body  of  the 
limestone,  rustv  clay  fillings  and  iron  stains.  In  these 
••  blanket."  bedded  deposits,  prospects  on  a  large  scale  may 


O'eZone 


OrrZ.oM\ 


If      t' 


I>I.ATK    XLVIII. 
Prospecting  with  hiamoiul  l>rill<. 

sometimes  ad\  aiitageouslv  be  done  bv  dr.lling  with  diamond 
drills  lioni  the  surtacc  down  through  as  many  of  the  strata 
as  are  suspected  of  being  ore  bearing,  the  "cores"  brought 
up  will  show  if  an  ore  bodv  has  been  penetrated  together 
with  its  apptoximate  thickness  at  a  certain  point,  and  if  this 
process  is  Continued  over  a  certain  area,  tne  approxiniate 
areal  limit  of  the  ore  body  may  be  ascertained.  This  work 
may  follow  upon  a  close  examination  t'lrst  of  mineral  signs 
along  the  outcrop.  It  is  sometimes  done  after  an  area  has 
been  exploited  for  some  time  bv  actual  mining  with  a  \iew 
of  fiisco\enng  new  bodies  or  continuations  of  the  ore. 


n 


TRUE    FISSl'RF.   VEINS. 

Whilst  profound  fault  cracks  may  be  filled  by  lava,  those 
not  dcscendinjj;  to  such  great  de[)ths  (Unibtless  lay  open,  till 
they  were  gradually  filled  by  solutions  carrying  in  earthy 
\ein-stone  and  metallic  matter;  in  a  word  they  were  the 
channels  of  mineral  or  hot  springs.  It  must  not  be  supposed 
that  these  fault  cracks  were  ever  "  open  chasms  "  commen- 
surate in  width  with  the  wide  dvkes  and  veins  now  fcnind  in 

them,  but  rather  in  some 
cases  very  close  fitting  cracks, 
mere  lines  of  weakness,  the 
walls  anpressed  closely  to- 
gether by  prodigious  lateral 
pressure.  In  other  cases  the 
fissure  would  be  rather  a 
shattered  /one  passing  down 
through  the  strata,  than  one 
definite  line  of  fissure.  Doubt- 
less when  the  molten  lava 
ascended  through  these  fis- 
sures it  greatly  wirlened  them 
to  admit  of  its  volume.  In 
the  case  of  true  fissure  \eins, 
the  fissure  or  shattered  xone 
was  enlarged  by  the  corrod- 
ing, substituting  power  of 
acid  mineral  solutions  till  we  have  to-day  a  fissure  \ein 
twenty  to  fifty  or  more  feet  in  width.  In  the  shattered  zone, 
this  substituting  process  would  go  on  easily  and   rapidly. 


Pi  ATK  XLIX. 

I>recciated  Lode  with  Quartz  Geodes. 


IMAIK     L. 
iUecciatcd  Vein. 


until  nearly 
mineral  i 


rly  all  the  shattered  fragments  were  replaced  bv 
natter  excef)t  a  few  "  imligestible  "  pieces,  which   if 


78 

■small,  would  cause  what  is  called  a  brecciated  vein,  and  if 
llarge,  "  horses  "  in  a  vein.   These  fragments  are  not  so  much 
pieces  that  have   fallen  from  abo\e    into   an    open    tissure 
gradually  lilling  up  with  solutions  of  (juartz  and  vein  matter 
in    which    they  became  entangled,  but  rather  undigested, 
lunsubstituted    fragments    (jf    the    wall    rock,    immediately 
.adjacent  to  the   fra"^monts,   for  at  times   stjme  line    in  the 
.fragment  corresponds  to  a  line   in   the  adjacent   wall   rock 
-without  evidence  of  any  serious  displacement.     Again,  the 
■shadowy  outlines  of  fragments  can   be  (observed  partially 
but  not  entirely  replaced  by  quartz  or  vein  matter.     Some- 
times the  "  breccias"  are  surrounded  by  rings  of  (|uartz  or 
inetal  and  called  "cockade  ores." 


i\ 


HOR.'^K.S. 

In  the  San  Juan  region  in  Colorado,  where  we  have  won- 
derful opportunities  of  obserx'- 
ing  extensi\'e  sections  of  great 
fissure  veins  descending  the 
faces  of  clitTson  either  side  of  a 
canyon  for  two  or  three  thou- 
sand feet,  such  broad  veins  at 
inter\-als  split  up  into  two  or 
three  arms  enclosing  large  frag- 
ments or  "  horses  "  oi"  the  la\a 
country  rock,  and  again  unite  to 
f(jrm  the  main  vein.  These  veins 
occupy  a  once  shattered  tissure, 
the  walls  (jf  which  were  origi- 
nally neither  straight  nor  regu- 
lar, \,  t  shattered  and  cracked. 
The  vein  matter  insinuated  itself 
between  the  shattered  portions, 
sometimes  fonuing  a  "  breccia  " 
of  small  fragments,  at  others 
"  horses  "  of  large  ones. 

The  appearance  of  these  great 
San  Juan  veins  from  a  little  dis- 
tance is  that  <jf  broad  yellow  stains  of  oxide  of  iron  con- 
trasted with  the  soml)re  gray  of  the  lava  rocks.  In  some 
places  in  this  region  the  (piartz.  by  reason  of  its  superior 
hardness,  stands  up  above  the  softer  lava  like  a  low.  rustv. 
or  white  wall.  Again,  at  other  localities  instead  of  being  a 
hold  outcrop,  the  \ein  is  represented   by  a  sharp,  shallow 


Platk  LI. 

Horse  or  Rider. 


7y 

depression  forininjj:  a  narrow  little  ra\ine  or  trench,  tiie  path' 
of  a  rivulet  and  zone  ot  abundant  Nftjctation.     In  this  case 
the  vein  was  full  of  decomposable   minerals,  such  as  pyrite 
whose  oxidation  decomposition  products  were  washed  out 
leaviinjj^  a  depression  in  the  rocks. 

So.  anionpst  some  oftiie  indications  of  a  lissure  \ein  to  tht^ 
prospector  we  may  note  : 

1st.  liroWM  or  jj;reen  stains  on  rocks. 

2d.    A  bold  (piartz  \ein  like  a  wall  above  the  country. 

3d.    A  narrow  ra\ine  or  ijulch. 

4th.  The    path    of   a    rivulet    and    e.xuberant    growth    of 
\'ef,'etation. 

SICN.S   OF    I'AII.TING. 

As  these  fissure  veins  are  ^'enerally  the  lillinjjf  of  fault 
cracks,  and  the  fissures  are  mainly  due  to  faultiiij.;.  a  pros- 
pector should  be  able  t<j  recojj^nize  the  surface  and  other 
si^rns  of  faultinjj;^. 

Faulting  as  we  have  said,  is  generally  the  result  of  extreme- 
folding.     So,  ill  entering  a  mountain  region  by  way  perhaps- 
of  a  canyon,  cutting  right  through  it  on  the  exposed  face  of 
the  dills,  he  may  observe  some  of  these  folds  or  arches,  low 
and  gentle  at  lirst,  but  gradually,  as  the  range  is  penetrated 
lurther,  increasing   in    sharpness,  steej)ness  and   closeness;, 
with  this  increase  we  may  expect  faults.     'I'he   presence  of 
the  fault  may  be  indicated  by  a  little  "  sag"  or  depression  in 
the  outlint' of  the  hill,  or  by  a  line  of   rubbish   aid   1  roken 
rock  descending  the  face  of  the  clilf,  or  by  a  /one  of  e.xuber- 
ant \'egetation,  or  by  the   pathway  of  a   little  rivulet,     lie 
will   obserxe  a  general   fractured  tendency  of  the  rocks  as 
they   approach    the    fault   line.     By  closer  search   he   may 
notice  nieces  of  rock  polished  or  slickensided  by  the  move- 
ment of^  the  walls  of  tlie  fault 
slipping  and  grinding  upon 
one  another.     Slickenside  is 
a  sure  proof  of  motion  ha\- 
ing  taken  place  in  the  rocks, 
and  is  often  observed  f)n  the 
walls   of    fissure    veins.      A 
miK  h  faulted  region  is  often 
marked   by  a  step-like  out-  Pi. All".  LII. 

line,     each      Ste|>     represent-  Vein  n  Faulted  by  Cross-Vein  B. 

ing  the   fallen   or   risen   side 

of  a  fault  block.     These  fault  lines  should  be  carefully  ex- 
amined for  mineral  indicati<jns,  especially  if  the  fault  line  is- 


O^ 


m 


iwi 


tt'^ 


tiniKJ 


T 


^ 


(/ 


V 


41 


80 


ocf.upicfl  l)y  a  porphyry  Hyke 
or  a  \'VA\\  of  (juart/  or  calrspar. 
Soint'timos  llicso  fault  lines 
an;  totally  harreii,  both  of 
rjtiart/,  N'c.'fiistonc  i<r  mctalli- 
Irroiis  matter.  Thry  may  be 
tillrd  )i|>  with  (lay.  itibbish 
and  broken  rock,  or  tin*  two 
walls  may  be  actually  wt'lded 
toj^rrther  by  pressure  accotn- 
panied  by  a  <-ertain  anw)unt 
of  heat,  producin/i,'  local  meta- 
morphic  action. 

l-'aultiiij.^   Joo   in  some    reg- 
ions mav  have  occurred  <on>- 
parati\('ly  recf  lUly,  or  at  least 
altiir  ihc  period  most  marked 
.|  by    deposit    of    mineral    solu- 
X  lions    .1(1.1    ore    deposits,     in 
;;^;^  which   c.fse   tin;   fissuies  may 
1-5 •-  be  I'l'vrtMi  or  at.  ptesent  occu- 
pi«Nl  l)y  hot  or  mineral  springs 
making'  \eins   lot    the   luture. 
A  stupendous,  comparati\ely 
njodern    faelt,  runs  alonvj  the 
west    base    of    the    Wahsatch 
mountains  in  ( 'tab,  its  line  is 
m. liked    l)\    a    S'-ries    of     hot 
sprin).;s. 

Aloiij^  the  lace  of  a  c.in- 
yon  wall  the  piosp«'ctor  may 
notice  some  peculiar  stratum 
near  the  top  of  the  dill  and 
its  counter[)art  out  of  placj' 
near  llur  bottom,  showinj.,'  that 
a  fault  has  oc«Mirred.  whose 
amount  of  slip  he  can  easil\ 
estimate  di  measure  ;  but 
when  a  fault  ol  many  thous- 
ands 1)1  feet  occurs,  a  knowi- 
(•(Ijjj,'  1)1  the  flifferent  j,^;«;olojri. 
I  a!  periods  in\'o|\e(l  in  the 
slip  is  necessary  to  estimate 
the   amount   of   lall.      I'liiis   il 


■3 
U 

c 

c 


U.    3 

r*   u 

V 

"3 
n 


8i 


a  prospector  by  his  j^eolof^ical  kiiowlt'rljrt;  should  rc('o)>;nize 
a  ("rctacoous  rock  hrouj^ht  up  jn  jIosc  juxtaposition  to  a 
Sihirian  rock  hi;  wouM  know  that  a  stup«'twlous  taulf  ha(l 
occurred  at  that  place,  involvinj;  the  entire  thickness  ot  the 
rocks  comnosinjj^  the  |)erio(ls  inlerveriinj^  between  the  Sil- 
urian and  tlie  Cretaceous. 

Tliat  a  faulted  rejj[ion  is  one  in  which  j.;reat  toUlin^  due  to 
lateral  tanjj^ential  prt-ssure  has  taken  plac«'.  th«'  folds  event- 
ually l)reakinj.»(lown  in  faults,  is  well  seen  in  tin*  structure 
of  the  .Mos(piito  r  ■  anj.je  in  South  Park.  Colorado,  which 
embraces  the  Lead\illf  inininjj;  district. 

Tlu'  comparatively  hoii/ontal  strata  ot  the  I'arkasthey 
a|)proach  the  .Mosquito  Kanj.»;e  brf^in  to  told  j^'Mitly.  thf  folds 
jj^raduallv  increasinj.(  in  steepness  and  closeness  as  they  a[>- 
proach  the  a.xis  (»f  the  ranj^c.  As  we  pass  up  I* our  Mde 
Canvoii.  which  shows  a  com|)lete  cross  s.-ction  ol  thv  ran^t", 
we  tind  the  axis  to  be  formed  by  a  maj^inficent  aiid  very 
st<'ep  arch,  well  shown  on  tin-  f;!ce  of  Sheep  Mountain, 
which  ha\inj.>[  arrived  at  its  utmost  tension  h)  i-aks  down  in 
what  is  called  the  London  mine  lault,  »ra\'ers'U|ij  and  split- 
ting the  ranj^e  lor  twentv  miles.  'I'he  line  ol  the  fault  is 
slidwii  b\  a  di'pression  bet  ween  Sh»' 'p  and  Lamb  .Mocilain, 
In  nearly  «'\ery  canyon  alonjj^  tlie  ',  ii»k  ot  •'us  ranj^'.  the 
line  of  the  faidt  is  easily  traced  by  siisiilo  arches  and 
'■  sa^s  ■  .ind  by  a  prcidiar  wa\v  loo,,  ol  the  Mule<i  stiaia  as 
they  bend  down  toward  the  lault.  An  we  penetrate  further 
across  t  he  ranj.je.  we  Dass  a  scries  of  -acli  faults,  each  one 
lormcrlv  re|)rrsenle''  bv  a  sl»'ep  li^i  that  pr«'<  edeij  ihf 
faultinj^'.  Hence  it  i  hat  we  descend  iiocu  the  toi>  of  this 
raii^'c  down  into  i  .id\ill«'  and  Ihf  Xik.-iisas  \'a(ley  l)y  a 
series  ol  ^ij^^antic  steps  or  ben^hrs.  e.u  ji  bench  lepresenl- 
inj^  a  tallen  faulted  block.  I''aults  have  thi-ii  |)oints  ol 
maxinuMn  dfplh  and  (list urbance.  from  whii  h  the\  aie  a|)t 
to  die  out  at  chrr  end  in  folds  or  rounded  hills.  iteat 
faults  are  acconijumid  by  minor  parallel  and  cross  faults. 

The  idtiiiiati;  tauseofthis  folflin^  ;Hid  faidt  in^  is  ;it  I  rib- 
uti'd  bv  souje  j.(eoloj.>[ists  to  the  inttnioi  ol  the  earth  j^rowin^ 
colder  aufi  contracting.  causinj.j  tiie  surface  crust  to  shrink 
and  fold  in  adaptinj.^  itstdf  to  tlie  shrinkin/^f  interior.  IMo- 
fessor  |.  K.  Kemp  sa)s  :  "The  strains  induced  i)y  coolinj.; 
and  contraction  of  tin;  earth  are  the  ujost  in>p<»rlitiif  caus«' 
of  fraclnre.  Tin-  contraction  (h'\tdops  .i  i.injrcntial  v,(i.iin 
which  is  ri'sisted  y  t  he  aifh-like  dispr>sition  ol  thecni-^t. 
Where  ther>'  is  insutlicient  supixut.  'gravity  causes  a  s  ij^r- 
j{inj.(  ol    the   m.deiial   into  t  rou^fis  or   syn<l!iial   foMs  whirh 


iff  T^i^dwcBiwMnf  jwwrn 


■•  ./ 


leave  (  orrcsp'Muliii)^'  arrlus  <>r  ;ii)f iclinal  (nWls  Ixiwrrn 
them.  WIric  tlit  laiij^i-iit iai  strain  is  j^ncak-r  than  tlie 
abilitv  of  the  Kuks  to  resist,  they  arc  u|)s«t  and  cruinplrd 
into  folds  ti.iin  (he  tliiust,  Hofli  kinds  of  l<,lds  inc  fnntfnl 
causes  of  liSMurinj;  cracks  and  j^n-ncral  sllat(^.•rill^^  and  c\cry 
slif)  from  vicldinjL,'-  sends  its  oscillations  abroad,  which  cause 
breaks  aloni^^  alllincs  of  wti'kness." 


i<irn\s. 

|oit>ts,  cnmnioii  Id  ail  ricks,  a|)])car  to  he  dne  not  so 
much  to  faulting  and  motion,  as  to  shrinka>,'e  o!  the  locks 
in  p.issinj.,'  from  a  soil  matl<'r  or  nuuldy  condition  to  one  of 
(  oiisolidatioi).  A  j4;ood  manv  so-called  lissiire  \fins,  v\vi\ 
in  the  j,,Manit<'  serii-s,  appear  to  occupy  extensi\'e  joint 
crac  ks,  rather  than  lanit  planes.  These  may  he  due  to  the 
general  shriidiaj'e  of  the  whole  mount. un  mass  in  consolida- 
ting^ from  a  sum;  (»lastic  or  a«pieo-i^neous  state  ol  soften- 
in;,,'  to  one  more  consolidated  and  ri^ifl. 

The  joints  in  l.iv.i  sheets  lomiin^^  curious  columns  like 
tiMJse  ol  IIk-  I'alisafles  ot  the  lliulon  are  flue  to  the  same 
shriMkay;e  lr<im  a  molten  stat-'.  Such  joints  n\a\  sometimes 
he  luinerali/ed  lor  a  short  dep.th.  forminjj;  what  are  called 
"j,jash  "  veins,  rather  than  true  fissure  veins.  'I'he  joints  in 
sedinientarv  rocks  are  i\\\c  to  consolidation  from  a  soft, 
mudd\,  imoherenl  ( onditifUi  ;  such  joints  may  similailv  he 
occupied  hy  '4;ash  veins,  or  may  lead  to  |)ockets  or  wide 
hlanket  deposits 

The  line  ot  weak  ness  hetwi-en  one  st  r.itum  (U' oiu"  set  ol 
strata  atul  another,  often  a  favorite  line  for  l)lanket  depos- 
its, is  due  to  one  stiatiim  heinjj^  first  l.iifl  down  and  partially 
consolidated  helore  the  i:e.\t  was  laid  later  on  lop  of  it. 


l-P 


i  ■  y 


i,mi'i<i.(;nati()N.s. 

Rocks  made  up  ol  loose  material  such  .is  porous  saiid- 
s'ones  .iiui  '(Mi^lonieK'.tes  are  soinejnies  permeati^d  hy  ore 
solutions,  as  loi  example,  the  "  Sil\-er-reef  "  sandstone  of 
Utali,  Sandstones  are  trecpiently  imprej^natc'fl  with  iron 
ami  copjUT  s'. litis,  In  tact,  if  we  (Oiisidei  that  ore  bodies 
were  (icpositefl  from  atpieous  solutions,  wr  have  onh'  to 
consider  the  \arious  opportunities  the  locks  atTorrl  by  their 
t»".\tnre.  structtis'e,  etc.,  fi»r  this  process.  \'eins.  in  a  woid, 
are  tilled  waterways  of  many  and  \arious  kinds. 


Ofy. 


8^ 


CHAPTI'R    VII 
VARIOUS  FORMS  Ol-   oKli-DlCPOSll  S. 

OUK    ItKDS.  • 

"Ore  l)c(ls  an-  inctallilcrous  drpMsitN  iiitrrsf rat iticd  hc- 
Iwffn  scdinu'ntai  \  rocks  ol  all  m'olojjfical  aj^t-s.  They  lie 
parallel  to  the  planes  ot  stmt  iticatioti  and  lollow  all  the  con- 
tortions ol  the  enclosin^j;  strata,  hence  they  are  thrown  ii\to 
lolds,  tronjjhs,  arches,  saddles,  oi  hasins.  The  upper  por- 
tions  of    the    arches    may    often    have    heen    renio\  ed    l)y 

erosion,  or  th«-  stiata 
n'.ay  he  faulted."  The 
or«'  deposits  or  heds  at 
Aspen  I  iccupy  a  tanited 
s\  nclinal  li  dd  or  hasin. 
The  enclo^i(l^  rock  is 
limestone,  in  p. lit  (\>  i|o- 
mitic.  At  Kead\ille  the 
deposits  occiipN  part  of 
a  si'ries  of  faulted  anti- 
clinal arches  and  syn- 
clinal t  roii).>hs.  ol  whiih 
tl;e  Mosipiito  ran).je  is 
the  main  .i.\is.  The  heds 
lie  hetweiMi  didomitii" 
limestone  and  sheets  of  |)orphvr\.  The  ore  heds  partake  of 
all  th«'  foldinj^,  faultiny^  and  olher  contortions  which  the 
enclosinj^:  rocks  ha\  e  sntlercd  in  the  uplie,i\al  ol  the  moun- 
tains. 

The  thickness  of  such  deposits  \aiies  much  and  may 
gradii.illy  thin  out  and  disa|>piMr.  hul  mav  also  (  ontinue 
loDf^;  enough  lor  all  mining  purposes. 

()ften  lliere  are  no  sh.iip  limits  between  an  ore  hetl  .md 
the  enclosing-  rocks,  oi  helwern  the  oic  hed  and  the  walls, 
it  walls  exist  at  all.  The  ore  appears  to  imjtre^nate  tlie  sur- 
rounding; rock  l)\  .1  (  lu-mical  inten  han^e  between  the 
elements  ol  the  rock  andllieor*-.  Such  .1  "  met.isoiuatic  " 
interchanj;*".  "  siibstilutioii,  "  or  •  leplactinent  "  appears  to 
have  taken  place  in  the  .iij^enlileious  le.id  deposits  ot  Lead- 
ville  and  ,\spen  brlween  the  ore  and  the  limestones. 

According  to  riiillips.  ••  .1  true  ore  bed  never  product's  a 
'Combed'  01   'ribbon     structure    m.idr    up    o|    symmetric.il 


IM.MK   MV. 

Kiiiillcd  Ore-liedH  in   Antii.'liniil  aixl    Sviuliti.il 


84 


h  :  i| 


II 


■n 


4i 


layers,  such  as  is  comiuun  in  so-called  '  true  fissure  veins, 
and  is  usually  without  the  crystalHne  texture  observable  in 

veinstones." 

INSI  KATiriKli    DKI'OSns.    USSIKK    VK.INS.    KTC. 

MifJeral  veins  are  chan^Hahle  in  character,  and  their  ap- 
pearances of  a  perplexinj4  and  complicated  nature.  There 
IS  a  j^'radual  passage  from  one  form  to  another,  so  that  it  is 
diflkult  to  classify  them.  There  is  often  no  such  sharp  dis- 
tiiKtio.i  between  one  form  of  ore  deposit  and  another,  as 
lej^'al  disputes  would  sonjetinies  demand,  and  a  witness 
should  hardly  be  called  upon  to  assert  on  oath  tha«  .such  a 
vein  is  a  '  iruc  fissure."  or  another  a  "bedded  \'ein,"  or  a 
third  a  "iegregated  vein."  "  Nature  abhors  straight  lines  ' 
anfl  sharp  »Mstinctions,  and  delights  in  blending  one  form 
i;Mperce()tibIy  with  another. 

I*hillips  di\ines  veins  into  two  classes.  "  regular  and  ir- 
regular veins."  "  Regular  uustrUifiefl  deposits  iiulude  true 
veins,  segngafffi  veins  and  gash  \eins.  Irregular  deposits 
include  impregnations,  fahlbanrls.  contact  and  chamber 
flenosits. " 

Veins  are  collections  of  mineral  matter,  often  closel)- 
related  to.  but  differing  more  or  less  in  character  from  the 

enclosing  country  rock,  usu- 
ally in  fissures  formed  in  those 
rocks  after  the  rocks  had  more 

or  less  consolidatffl. 
All  \'eins  fio  not  carry  metals; 

some  are  merelv  l)arren  (|uartz, 

fildspar,  or  calcspar.  like  the 

b.irren   veins  we  so  oficn  see 

tr;«versing granite  or  limestone 

rocks. 

\'eins  may  divide.  "  split  up  " 

or  thin  out,  and  are  irregular  in  shape  and  structure,  owing 

to  the  irr«*gular  width  ot  the  fissures  and  to  other  causes. 


PIAIK    LV. 
A  Split  Vein, 


DKII.MTloN    (»F    MININd    rKHIVIS. 

The  rock  in  whicli  a  vein  is  found  is  called  the  "country 
rock."  <•.;'..  liinestfMu-.  granite,  norplnrv. 

The  [xMtions  of  countty  rock  in  t'linct  contact  with  tlie 
vein  are  called  respectiv«'ly  the  "hanging  wall,"  or  roof, 
and  the  "fool  wall  '  or  floor.  This  is  onlv  in  inclined  or 
flat  \eins.  as  a  vertical  fissure  vein  can  have  neither  roui 


«$ 

nor  floor,  but  only  two  walls,  east  and  west,  or  north  and 
south,  according  to  the  coinnass.  The  inclination  of  a  vein 
to  the  horizon  is  its  "dip.  The  horizontal  direction  of  a 
vein  at  rijjht  angles  to  its  dip  is  its  "strike."  The  latter 
may  commonly  he  observed  alonjj;  the  surface  outcrop,  the 
f(irmer  either  in  the  workings  ot  the  mine  ()r  where  the 
vein  is  exposed  on  the  side  of  a  canvon. 

Roth  dip  :ind  strike  of  a  \ein  often  vary  much,  the  former 
with  depth,  the  latter  with  extension  across  the  country. 
A  vein  or  ore  deposit  will  not  unfrecpiently  bej.jin  with  a 
j.,'entU'  dip.  and  increase  rapidly  in  steepness  with  depth. 
The  ore  fleposits  on  As|)en  Mountain  commonlv  bej^jin  with 
a  din  of  25  .  and  at  a  depth  of  less  than  a  thousand  feet 
reach  (o  or  more. 

As  tissure  veins  commonly  occupy  fault  lissures.  their 
irrefjularities  in  dip  and  strike  corresp(»nd  to  those  we  have 
already  spoken  about,  under  faults. 

The  anj.fle  of  dip  is  usually  taken  from  its  variation  from 
a  horizontal.  Mot  a  perpenflicular  line.  Thus  a  dip  of  75" 
means  one  th;it  is  very  steep,  while  one  of  10'  is  a  gentle 
inclination. 

A  laver  or  shee'.  of  clay  called  " j^^oujj^e."'  or  sel\aj.je.  often 
lines  oiu'  or  both  walls  of  a  vein  between  the  country  rock 
and  the  jjangue  or  \'ein  pr(>per.  It  is  deri\i'd  from  the  ele- 
ments of  the  adjacent  country  rock.  decom|)osi'd  by  water, 
and  sometimes  by  the  friction  of  the  walls  of  the  fissure 
ajj;ainst  one  another,  or  aj^jainst  the  \-ein  matter,  in  the 
jirocess  of  sli|)pinj.j  and  faulting.;.  whii"h  is  often  shown  by 
Its  being  smoothed,  "  slickensided."  j)olished  »)r  groo\ed. 
(Joiige  often  contains  some  rich  decompc^ed  mineral  in  it. 
such  as  siilphiirets  of  silver.  It  sometimes  occurs  in  the 
heart  of  a  vein,  especially  if  that  vein  has  been  re-opened 
anew  by  mowments  of  the  strata.  The  "  riiinese  Tallow  " 
gouge  of  Leadxille  results  from  the  dec(tm|)osition  of  the 
leldspars  in  the  adjacent  white  porphyry,  and  is  a  hydrous 
silicate  of  alumina. 

ill  the  granite  \eins  in  Clear  Creek  County  the  gouge  is 
(ierixt'd  from  the  feldspars  of  the  grai  ite.  (iouge  is  some- 
times useful  in  defining  the  limit  of  th  •  \ein  between  walls, 
t  bus  preventing  unprofitable  exploratioc  into  the  "  country." 
it  is  alsd  a  guide  for  following  down  a  vein  when  mineral 
and  gangue  may  be  wanting  or  obscure. 

Moth  walls  are  not  always  clearly  detined  by  slickensided 
surfaces,  by  gouge  or  other  mark,  and  s(j  at  times  the  vein 
is  lost. 


*i»«i^i**'«*'«»« 


I'  '1 


I 


hi  i 


86 

False  walls,  catiscf!  by  movements  in  the  adjacent  strata, 
by  joints,  utc.  also  niisluad. 

It  is  not  uncommon  tor  a  tissure  vein  to  have  but  one 
clearly  defined  wall,  the  other,  if  it  exists.  bein>f  obscured 
or  chanfj^ed  by  mint-ral  solutions.  Sometimes  two  cracks 
(»r  fissures  occur  parallel  to  ea«  h  other  anrl  the  inter\eninvi: 
country  rock  has  been  altered  and  mineralized  into  a  vein. 
It  is  Mobably  in  this  way  that  many  wide  veins  were 
tormer . 

Mr.  amnions  has  fr)und  that  fissures  are  formed  by  jijreat 
movements  of  the  earths  crust  <tr  by  local  contraction  of 

the  rocks,  and  that  a  tissure  is  not  neces- 
sarily one   with    well  defined  walls  at 
considerable  distances  apart,  tillefi  after 
the  fornuation  of   the   tissure.  but  tli.it 
the  ordinary  cracks  or  joints  in  f.jranite 
(piarries.  e.\teiulinf.f  rejj^ularlv   to  j.jreat 
len/.(ths  ordepths.  illustrate  the  orij.final 
\       W/\^''       fissures   which   have  been  chanj^^ed  by 
\\.''f/^    y-^-—       percolating.^  waters  carryinj.^  mineral  so- 
''-      ^  lutions  into  \eins  anrl  di-posits  ol  ore. 

In  all  crystaline  anrl  sedimentary  rocks, 
these  cracks  or  joints  run  parallel  to 
each  other  at  various  dist.mces  apart, 
often  plentiful  and  close  toj^ether.  In 
cases  where  percolatinj^;  waters  wert; 
char>.fefl  with  the  proper  metals  atid 
veinstone  matter  and  the  necess.iry 
chemical  anrl  physical  conditions  existed,  the  rocks  lyin^; 
between  those  cracks  or  joints  were  altered  into  ore. 

As  one  element  was  dissoKed  anothe-r  took  its  place,  so. 
accordiiif^  to  this  auth<»rity.  it  would  seeni  that  e\en  a  list;ure 
vein  may  be  only  a  sort  of  "metasomatic  replacement  "  of 
rock  by  mineral.  Hence  what  is  commonly  accepterl  as  a 
"  wall  "  of  a  vein,  is  not  necessarily  one.  and  cross-cuttinj.;. 
in  order  to  determine  the  lateral  boundaries  c,f  the  ore.  is 
safer  than  to  rely  on  supposed  walls.  A  so  called  "slip" 
has  often  been  followed  by  a  miner  as  a  supposed  wall,  until 
by  accident  he  broke  throujj[h  and  found  irood  (ire  on  the 
other  side.  If  \eins  are  formed  accordinjj^  to  Mr.  l-'-mmons" 
theory,  the  occasional  loss  of  one  or  both  walls  is  easily 
accounted  for. 

Cross  veins  of  a  more  recent  af^e  sometimes  cut  or  lault 
an  older  vein.  The  point  of  intersection  is  generally  rich  in 
mineral.       Cross    \eins    must    not     be    confounded    with 


Pl.ATI.   LVI. 

IinpreiinatiDn  of  Kock  t>y 
Vein. 


87 

"  leaders,  "  whiv-h  arc  tln'  iillinj^'  ni  iniintr  cracks  rxtoiulinj^^ 
off  from  tlu'  \i  it),  anfl  ari'  sonutiinfs  MiHicifiit  l\  profit. il)l«'  to 
work.  Wliilc  llicy  somctinifs  Ir.id  a  |)ro>|»«'(tor  to  the 
main  vein,  they  may  also  lead  a  miner  miderj^^romid  astray 
from  tin-  true  \iin. 

The  spliltiiij^'  of  ;i  \t  in  by  .i  "  horse  "  or  lar>;e  frai^ment  ol 
the  country  lyinj.(  in  the  vein,  may  he  mistaken  for  a  true 
cross  vein,  or  the  orif.;inal  fr.ictiire  of  the  fissiuf  mav  have 
been  in  the  form  of  a  star  or  like  llie  spokes  ot  a  wheel  radiat- 
ing.; to  the  huh. 

In  such  cases  there  are  no  true  cross  xcins.  Hut  when,  as 
in  the  San  Juan  district,  we  ha\e  two  well  diliiu-d  sets  ol 
veins,  one  strikinjj^  northeast  by  southwest,  and  the  other 
northwest  bv  southeast,  they  «ut  each  other  diagonally, 
the  cut  \'ein  l)eiiij.j  the  older,  'ihesc  o|)posite  sets  ol  \eins 
ha\e  been  formerl  at  different  times.  .M.inv  contain  a  char- 
acteristically ditlerciit  class  or  \ariety  ot  minerals.  Thus  in 
Cornwall,  Kii^land,  one  set  carries  tiii  and  the  other  K'ad. 

si(;ns  Of'  .\   rKir  iissi  hk  vi.in. 

True  fissure  veins  show  si^ns  of  motion  or  slip|)inf;  on  the 
sides  ol  the  lissure,  such  as  slickeiisides.  j,;ou>.je,  crushed 
walls.  '•  horses,"  or  "  breccia," 
the  latter  Ix'inj^  small  por- 
tions oj  the  Country  n'ck 
surrounded  and  cemente(f  by 
\ein  matter.  In  the  Coiii- 
stock.  the  (piart/  is  f.(round' 
to  powder,  riu-  vein  itself, 
thoiij^'h  occupying.;  a  healed 
fault  lissuri',  may  be  itself 
faulted  by  later  movements 
in  the  mountain  aft»'r  the  vein 
was  formed.  Soiiu- of  the  lis- 
sure veins  on  Knj.;ineer  .Moun- 
tain. San  luan,  are  so  dislo- 
cated. 

The  vein-filled  fissures  be- 
\u^  a  line  of  weakness,  may 
be  re-opened  by  mountain 
movements,  ajul  other  or  flif- 
ferent  combinations  of  ore  in- 
troduci'd  into  the  heart  of  the  vein.  Such  a  reop'jninj,' 
would  be  marked  by  a  succession  of  "combs"  or  banded 
ribboti-like  deposits  of  nrv,  and  by  j,j(iuj.je  matter. 


Pi.  AT  I    LVII. 

Combe<l,  Ilaiulcil  or  Ribbon  Siriictiirc 
wiih  (Juart/  (•ende. 


IMAGE  EVALUATION 
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OUTCROP  OF  VEINS. 

The  outcrop  of  a  vein  is  that  which  appears  at  the  surface 
and  usually  attracts  prospectors  to  the  spot.  Sometimes  it 
may  be,  as  in  the  San  Juan  district,  a  bold  v^ein  of  hard 
white  or  rusty  quartz,  standing  up  in  relief,  by  its  superior 
hardness,  above  the  surrounding  countr}^  like  a  low  wall. 
Or  again,  in  the  same  district,  from  being  composed  ot 
softer  or  more  soluble  substances  than  the  prevailing  erup- 
tive lava  sheets,  instead  of  a  wall  it  causes  a  depression  or 
trough  on  the  side  of  a  hill,  forming  the  pathway  tor  a  rivulet 
and  marked  by  luxuriant  vegetation.  Commonly  the  out- 
crop consists  of  a  decomposed  mass  of  rock,  stained  with 
oxide  of  iion  and  streaked  here  and  there  with  green  or  blue 
carbonate  of  copper,  and  is  called  "  float  "  or  "blossom  "  by 
the  miners.  This  "  float "  is  the  chemically  changed  or 
oxidized  portion  of  the  true  and  unchanged  vein  lying 
deeper  below  the  soil.  On  Aspen  Mountain  the  float  is 
generally  a  rough  crystalline  mass  of  calcspar  and  baryta 
stained  with  iron  and  copper. 

In  this  "blossom  rock"  free  gold  is  not  unfrequently 
found,  but  unaltered  sulphides,  such  as  galena  or  iron 
pyrites,  are  rarely  mei  with  on  the  outcrop.  In  the  San 
Juan  district,  on  Mineral  Point,  we  have,  however,  found 
galena  at  the  grass  roots,  and  broken  off  large  chunks  of  it 
from  a  quartz  vein  outcropping  on  the  surface. 

In  gold-bearing  veins  such  an  oxidized  condition  is  desir- 
able it  it  continues  down  to  any  depth,  for,  so  far  as  it  con- 
tinues, the  gold  is  free,  and  the  ore  is  a  free  milling  one, 
easily  treated,  and  often  exceedingly  rich  in  gold,  as  in  the 
celebrated  Bowen  mine  of  Del  Norte ;  but  as  soon  as  the 
hard  white  quartz  and  the  unoxidized  pyrites  of  the  true 
vein  is  reached,  the  ore  is  no  longer  free  milling,  but  must  be 
smelted.  The  gold  may  still  be  found  free,  perhaps,  in  the 
hard  quartz,  but  if  the  pyrites  should  not  prove  ricn  in  gold, 
the  palmy  days  of  the  mine  may  be  considered  as  past. 
Many  such  rich  deposits  on  the  surface,  abounding  with 
specimens  of  free  gold,  have  proved  great  disappointments 
with  depth. 

WIDTH   OF   VEINS. 

Veins  may  vary  in  width  or  thickness  from  a  half  inch  to 
a  hundred  feet.  They  also  pinch  or  widen  at  intervals  in 
their  downward  course.  The  widest  "mother"  veins  are 
nOt  always  the  most  productive,  though  they  are  very  per- 


■'a  I 


I 


89 

sistent  in  length,  and  we  may  suppose  in  depth  also.  In  the 
San  Juan  district  the  "mammoth"  veins  of  quartz,  often  a 
hundred  feet  wide,  are  not  the  favoriies  for  development, 
the  ore  being  found  too  much  scattered  in  them,  and  the 


HS 

■  .f-  > 

/:•••■ 
11'-  • 

'^"'^ 


^yfilfciii'^ 


Plate  LVIII. 

Metalliferous  Veins  Exposed  to  View  near  Howardsville,  San  Juan,  Colorado. 
Showing  Two  Systems  of  Fissure  Veins  Crossing  One  Another. 

development  less  easy  than  in  those  10,  20  or  30  feet  wide, 
where  the  metal  is  more  concentrated.  These  mammoth 
veins  in  the  San  Juan  are  easily  traceable  for  miles  over  the 
surface   of  the   country   and  down  the   sides   of  the  deep 


m 


I;;' 


90 


II' 


[Is   : 
P    ' 


M 

hi 


canyons.    Their  limiting  depth  has  never  been  reached,  and 
probably  never  will  be  by  mining. 

DEFINITION   OF   TRUE    FISSURE   VEINS. 

True  fissure  veins  are  popularly  defined  as  filling  fissures 
of  indefinite  length  and  depth,  commonly  occurring  in  paral- 
lel systems,  traversing  the  surrounding  rocks  independent 
of  their  structure  or  stratification,  and  commonly,  though 
not  necessarily,  at  an  angle  different  from  that  of  the 
stratification — in  other  words,  cutting  across  the  planes  of 
stratification.  These  veins  originated  in  fissures,  not  neces- 
sarily wide  open  ones,  but  on  the  contrarj-,  rather  narrow 
,.  ^^^  cracks   descending,   however, 

to  great  depth  such  as  those 
produced  by  faulting,  or  the 
general  cleavage  lines  of  the 
mountain.  The  latter  may  be 
frequentl)^  observed  in  every 
canyon,  and  also  in  the  sedi- 
mentar)'  rocks  of  the  foot- 
hills and  even  along  the  flat 
surfaces  of  the  plains.  They 
Plate  LIX.  ^re   very  conspicuous  in  the 

Fissure   Vein   Conforming  in    Part   to      plains     arOUnd    Trinidad,    and 

in  p^rfSsing  them.^  ^'""'^''''°"'     ^^'^    there    not    unfrequently 

occupied  by  a  series  of  narrow 
parallel  dj'kes  of  basalt  instead  of  by  mineral  veins.  Cleav- 
age lines  or  joints  are  familiar  to  every  stone-quarry-  man. 

These  cracks  are  caused  by  extensive  movements  of  the 
earth's  crust  in  the  process  of  mountain  uplift,  and  also  on 
a  smaller  scale  by  coi:traction  of  the  rocks  in  cooling  from  a 
heated  or  molten  condition,  or  even  in  consolidating  from 
a  soft  or  muddj'  condition. 

The  two  walls  enclosing  a  vein  do  not  generallj^  coincide, 
as  might  be  expected,  if  the  vein  occupies  a  line  of  fault.  A 
true  fissure  vein  may  in  some  part  of  its  course  coincide 
with  the  dip  of  the  surrounding  strata.  As  the  plane  of 
stratification  or  line  of  division  between  one  stratum  and 
another  is  a  natural  line  of  weakness,  a  crack  once  started 
would  be  liable  to  follow  it  for  some  distance.  And  when 
uplift  occurs  such  places  are  liable  to  slip  one  upon  the 
other,  and  a  true  parting  fissure  ensues  conformable  to  the 
prevailing  dip.  Such  a  vein  might  appear  at  first  to  belt^ig 
to  the  class  of  so-called  "bedded  veins,"  but  if  with  depth 


9* 

it  should  be  discovered  to  be  cutting  across  the  strata  it 
would  be  pronounced  a  "true  fissure  vein."  The  appear- 
ance of  slickensides  or  other  signs  of  motion  on  the  walls  of 
the  apparently  "  bedded  portion  "  would  then  prove  it  to  be- 
long to  the  "true  fissure"  class,  and  that  actual  Assuring 
had  taken  place  prior  to  the  vein-filling. 

CAUSK   OF   POCKETS   IN    FISSURE   VEINS. 

As  a  fault  fissure  in  its  downward  course  usually  pursues 
a  zigzag  rather  than  a  straight  course  with  smooth  surfaces 
on  either  side  of  the  crack,  the  inequalities 
of  one  face  of  the  crack  are  brought  into 
opposition  to  the  inequalities  on  the  other 
face,  as  one  or  the  other  side  of  the  fault 
slips  up  or  down,  and  thus  are  produced 
pinches  and  wide  cavities,  which  give  rise 
to  the  "pinches"  and  "  bonanza  pockets" 
so  common  in  fissure  veins.  A  so-called 
true  fissure  vein  may  sometimes  have  ad- 
vantages over  some  other  forms  of  vein 
occurrence,  from  its  persistency  and  com- 
parative regularity  to  great  depths.  It 
must  not,  however,  be  expected  that  it 
will  continue  equally  rich  or  equally  poor 
throughout  its  course.  There  may  be  com- 
paratively barren  spots  and  rich  spots, 
pinches  and  widenings,  local  combinations 
of  richer  or  poorer  varieties  of  mineral. 
But  the  vein  as  a  rule  is  not  likely  to  en- 
tirely give  out. 

RICHNESS   WITH   DEPTH. 

There  is  no  scientific  reason  why  a  vein 
should  "grow  in  richness  and  size  with 
depth."  This  is  a  popular  fallac}^  originat- 
ing from  the  now  less  accepted  theory  that 
veins  were  formed  by  the  precipitation  of 
precious  metals,  by  heated  rising  waters  or 
vapors,  and  hence  that  the  greater  con- 
centration would  take  place  at  greater 
depths.  The  "lateral  secretion"  theory, 
now  by  some  accepted,  ascribes  the  deposition  of  ore  to 
solvent  waters  reaching  the  vein  from  ground  quite  near  to 
it  and  coming  naturally  from  above  and  the  sides  quite  as 
often  as  it  is  ejected  upward  by  pressure  from  below. 


Plate  LX. 

Pocket  and  Pinches 
Resulting  from  slip- 
ping_  of  uneven  Walls 
of  Fissure. 


i  !^ 


i    ! 


92 

In  Idaho  Territory,  says  Mr.  A.  Williams,  "the  rule  is 
rather  that  veins  grow  less  rich  and  strong  with  depth, 
though  strong  veins  may  continue  metalliferous  to  a  greater 
depth  than  mining  can  ever  reach. 

"The  thickness  of  the  earth's  crust  which  we  are  able  to 
explore  is  very  limited.  Increase  of  heat,  as  in  the  deep 
Comstock  mine,  and  other  natural  difficulties,  limit  us  to  a 
few  thousand  feet — 3,000  at  most.  These  deep  mines  have 
not,  as  a  rule,  proved  richer  with  depth,  but  to  the  contrary. 
Some  veins  have  been  worked  through  alternate  zones  of 
richness  and  barrenness.  The  Comstock,  which  has  been 
opened  for  four  miles  in  length  and  to  a  depth  of  3,000  feet, 
shows  the  ore  bodies  to  be  scattered  irregularly  and  the 
barrenest  ground  is  at  the  bottom.  On  the  other  hand 
some  of  the  most  celebrated  mines  derived  their  wealth 
from  rich  ores  encountered  near  the  si'rface  and  have 
proved  most  disappointing  with  depth." 

Atmospheric  action  for  a  long  period  has  often  reduced 
the  ore  to  its  richest  compound,  and  when  the  hard  material 
is  reached,  leanness  sets  in.  This,  as  we  have  observed,  is 
commonly  the  case  with  gold  veins.  The  richness  of  the 
Leadville  mines  is  derived  from  their  decomposed  com- 
pounds. Again,  as  the  surface  crust  can  be  so  little  ex- 
plored by  mining,  it  is  to  be  remembered  that  the  erosion 
by  glaciers  and  waters  has  already  removed  thousands  of 
feet  of  the  vein,  so  that  we  are  able  to  examine  only  a  small 
fraction  of  it,  while  an  unknown  quantity  lies  in  the  depths 
below.  If  these  veins,  then,  continue  to  the  supposed  great 
depths  below,  we  are  vary  far  from  their  starting  point,  and 
erosion  having  removed  their  upper  portions,  we  cannot 
find  their  surface  finishing  point;  in  other  words,  it  is  not  a 
fresh  "  ready  made  "  vein  we  find,  but  portions  of  an  old 
vein  already  extensively  mined  by  the  processes  of  nature. 

So  far  as  our  experience  goes  in  Colorado,  after  a  moder- 
ate depth  is  reached  below  surface  action,  or  below  the 
"water  level,"  a  fissure  vein  may  grow  richer  or  poorer, 
wider  or  narrower  with  depth,  without  any  law  except  local 
experience  in  a  district. 


VEINS   IN   GROUPS. 


Fissure  veins  occur  in  clusters  and  nearly  parallel  groups, 
forming  a  mining  district,  and  again  in  that  district  certain 
peculiar  veins  may  be  grouped  together,  forming  a  "  belt." 
Thus  Boulder  district  occupies  a  certain  isolated  area,  out- 


93 

side  of  which  few  mineral  deposits  occur  for  a  long  distance. 
We  have  also  in  that  district  several  distinct  belts  carrying; 
different  characteristic  ores,  such  as  the  telluride  belt, 
marked  by  rare  telluride  deposits,  the  pyritiferous  gold- 
bearing  belt,  and  the  argentiferous  galena  belt.  The  Central 
City  region  is  characterized  by  auriferous  pyrites  belts. 
Georgetown  district,  not  far  distant,  by  argentiferous  belts, 
and  Idaho  Springs,  lying  between  the  two,  by  both  gold  and 
silver  belts. 


CHAPTER  VIII. 


RELATION   OF   VEINS   TO   ERUPTIVE   FORCES. 

The  ultimate  cause  of  the  richness  in  veins  of  a  district  or 
locality  is,  that  local  dynamic  and  eruptive  forces  were  more 
energetic  there  than  elsewhere,  causing  great  disturbance  of 
the  rocks,  accompanied  b)'  fissures,  and  eruptions  of  por- 
phyry. 

Thus  at  Leadville,  the  Mosquito  range  is  violently  folded 
and  fractured,  eruptive  rocks  have  issued  abundantly,  and 
associated  with  such  phenomena  we  find  great  lead  and 
silver  deposits. 

Further  south  the  great  San  Juan  district  is  split  up  in  an 
extraordinary  manner  with  great  fissure  veins.  The  region 
is  an  eruptive  one,  consisting  of  prodigious  flows  of  eruptive 
rocks  traversed,  not  unfrequently,  by  newer  eruptive  dykes. 

In  the  Gunnison  district  the  strata  have  been  overturned, 
disturbed,  folded  and  faulted  in  an  extraordinary  manner  by 
the  intrusion  of  great  masses  of  eruptive  rock  forming  the 
peaks  of  the  Elk  Mountains.  The  strata  everywhere  are 
riddled  by  dykes  or  intrusive  sheets,  and  the  evidence  of 
heat  is  apparent  in  the  general  metamorphism  of  the  entire 
region.  Mineral  veins  abound.  The  same  phenomena  are 
repeated  more  or  less  in  the  neighboring  region  around 
Aspen,  and  at  Pitkin  and  Tincup. 

At  Boulder,  Central  and  Georgetown  there  is  a  concentra- 
tion of  eruptive  dykes  locally  in  each  district,  and  few  dykes 
or  eruptive  rocks  outside  of  those  districts.  On  the  other 
hand  we  have  no  ore  deposits  in  the  undisturbed  rocks  of 
the  plains  or  the  flat  basins  of  our  parks,  and  notably  our 
mining  districts  are  for  the  most  part  well  into  the  core  of 
the  mountains,  where,  in  the  natureof  things,  folding,  crump- 


i 


94 

ling,  faulting,  eruptions  and  metam<:)rphic  heat  were  more 
energetic  than  along  the  flanks  and  foothills  of  the  range 
which  have  usually  pnjved  unproductive. 

The  older  eruptive  rocks  such  as  the  quartz,  porphyries 
and  diorites  of  tne  Leadville.  South  Park  and  Gunnison  dis- 
tricts, are  more  favorable  to  the  production  of  ore  deposits 
as  a  rule,  than  the  more  modernly  erupted  lavas,  such  as 
basalt  or  dolerite  which  we  commonly  find  occurring  in  dykes 
and  surface  overflows,  traversing  or  capping  our  Cretaceous 
and  Tertiary  c<jal  fields  al(jng  the  foothills  as  at  the  Table 
Mountains  at  G<jlden  and  Trinidad. 

Some  of  the  lighter  colored  and  somewhat  recent  la\-as 
like  the  tufaceous  rhvolite,  which  caps  so  many  of  the  Ter- 
tiary mesas  on  the  Divide  between  Denver  and  Colorado 
Springs  have  also  hitherto  pro\ed  barren.  Vet  the  volcanic 
rhyolites.  andesites  and  phonolites  of  Silver  Cliff.  Cripple 
Creek  and  Creede  are  productive  of  both  gold  and  silver.  A 
large  portion  of  the  eruptive  rocks  of  the  San  Juan  region, 
productive  of  gold  and  silver  bearing  fissure  veins,  are  in 
andesitic  breccias  of  comparatively  modern  date.  The  older 
eruptive  rocks,  as  we  have  stated,  are  nearly  all  of  an  intru- 
sive character,  never  having  reached  the  surface,  while  the 
newer  ones  bear  evidence  of  having  flfjwed  over  the  country 
like  modern  lava  streams,  as  is  shown  by  spongy  scoria  on 
their  surface,  and  may  be  called  "eflfusive." 

In  Colorado  the  ore  body  is  not  usually  found  in  the  heart 
of  an  eruptive  sheet  or  dyke  of  porphyry,  so  much  as  at  the 
line  of  its  contact  with  some  (jther  rock,  such  as  limestone, 
granite  or  gneiss. 

CON  lACT    DEPOSITS. 

The  "contact "  ore  deposits  of  Leadville  occur  at  the  con- 
tact of  quartz,  porphyry  and  dolomitic  blue  limestone. 

Some  of  the  veins  at  Boulder.  Central  and  Georgetown 
are  at  the  contact  of  porphyry  and  granite  or  gneiss. 

Exceptions  occur,  however,  where  mineral  is  found  either 
in  the  heart  of  a  dyke,  or  the  whole  dyke  may  be  so  impreg- 
nated as  to  Constitute  in  a  sense  a  vein.  These  exceptions 
are  generally  confined  to  pvritiferous  gold  deposits,  and 
telluride  gold  deposits  as  at  Cripple  Creek. 


GOLD-BEARIXG    DYKES. 


Suppose  a  dyke  or  mass  of  eruptive  r<3ck  to  be  thoroughly 
impregnated  with  gold-bearing  pyrites.     Near  the  surface 


95 


and  (jften  for  a  Cwnsiderabic  deptli  the  rock  is  dec xnposed 
and  the  pyrites  oxidized  into  rusty  iron  ore.  Hberatin^;  the 
gold  which  is  entangled  in  the  "gossan  '"  in  wires,  tlakes  or 
even  small  nuggets.  As  long  as  this  decomposed  or  o.xidized 
state  continues,  the  ore  is  tree  milling,  but  with  depth  the 
dyke  is  lound  in  its  primiti\x'  hardness,  studded  with  iron 
pyrites  which  may  or  may  n<:)t  pro\e  rich  enough  for  the 
more  e.\pensi\-e  treatment  of  smelting.  Such  gold-bearing 
dykes  are  found  at  Breckenridge.  South  Park,  also  in  Idaho 
Territory.  Cripple  Creek.  Colorado,  and  in  old  Mexico,  and 
many  other  gold-bearing  regions. 

The  Printer  Boy  gold  mine 
at  Leadville  is  a  vertical  de- 
posit in  a  jointing  or  fracture 
plane  in  a  dyke  of  quartz-j")<>r- 
phyry.  rusty  and  much  decom- 
posed near  the  surface  where 
it  yielded  free  gold;  with  depth 
this  passes  into  copper  and 
iri)n  pyrites.  The  vein  is  fri)m 
an  inch  to  f(jur  feet  in  width  ; 
stringers  carrying  ore  extend 
into  the  porphyry,  which  is 
highly  charged  with  pyrites 
which  doubtless  supplied  the 
\-ein  with  mineral  throusfh  the 


Platk  LXI. 


Gold  Vein  or  Gold  Bearing  Dyke, 
showing  Oxidized  and  Unoxidized 
Portions. 


agency  of  surface  waters.  In 
Arizona,  near  Prescott.  at  the 
Lion  mine  we  find  a  green 
dyke  of  eruptive  diorite  penetrating  granite.  This  dyke  is 
traversed  by  numerous  small  veins  of  white  quartz  which 
near  the  decomposed  and  rusty  surface  are  rich  in  free  gold. 
At  slight  depth  tlie  quartz  \-eins  become  charged  with  unox- 
idized iron  pyrites  sutficiently  rich  in  gold  to  merit  treat- 
ment by  smelting.  The  surface  ore  is  treated  by  a  simple 
•' arrastra."  and  is.  of  course,  free  milling.  The  gold  seems 
to  be  mostly  confined  to  the  quartz  veins. 

FISSURE   VEIX.S    IX    IGNEOUS    AND   GRANITIC    ROi.  l-LS. 

The  San  Juan  district  is  an  exceptional  case  where  im- 
mense numbers  of  fissure  veins  penetrate  igneous  eruptive 
sheets.  The  fissure  veins  consist  of  hard  gray  jaspery 
quartz,  traversing  lawi  sheets  whose  united  thickness  is  from 
2,000  to  3.000  feet.  The  veins  produce  lead,  bismuthinite, 
gray  copper  and  other  sih'er-bearing  (tres. 


96 

In  Colorado  true  fissure  veins  are  most  characteristic  of 
the  Archa-an  granitic  series.  In  fact,  all  the  veins  in  that 
series  are  fissure  veins.  Locally  they  (Kcur  as  in  the  San 
fuan,  cutting  through  eruptive  f(Kks.  Outside  of  these 
"formations  few  true  fissure  veins  occur. 

An  exception  may  be  made  of  the  Gunnison  and  Elk 
Mountain  region  where  the  fissures  traverse  all  the  forma- 
tions from  Arcluean  granite  t(j  the  top  of  the  Cretaceous 
coal  beds.  Nearly  all  other  mineral  occurrences,  such  as 
those  in  the  limestone  regions,  come  under  the  class  of 
bedded-veins  or  blanket-veins,  pipe-veins  or  "pockets"  and 
show  none  of  the  characteristics  of  slipping  motion  or  fis- 
sure action.  Under  this  latter  class  the  Leadville  and  As- 
pen deposits  may  be  grouped. 

Ore  deposits  commonly  occur  at  the  junction  or  contact 
of  two  dissimilar  rocks,  as  between  (luartzite  and  limestone 
or  limestone  and  dolomite. 

Lodesoccur  also  between  the  stratification  planes  of  the 
same  class  of  rock,  sandwiched  in  between  two  layers  of 
limestone,  and  sometimes  impregnating  the  layers  (jn  either 
side  for  some  distance  from  the  dividing  line  between  the 
two  strata,  which  is  commonly  the  line  of  principal  ci^ncen- 
tration  of  ore,  and  often  descend  from  tnis  concentration 
line,  through  the  medium  of  cross  joints,  to  form  large 
pockets  in  the  mass  of  the  limestone.  The  Aspen  and 
Leadville  deposits  are  of  this  character.  Also  when  (jre 
bodies  occupy  a  true  fissure,  /.  <?.,  one  cutting  across  the 
stratification  planes,  they  may  locally,  for  a  short  distance, 
impregnate  the  adjacent  walls  or  country  rock  more  or  less. 
C>ur  fissure  veins  in  granite  and  gneiss  often  impregnate 
the  walls  to  a  small  extent. 

Mineral  deposits  favor  as  a  rule  the  older  rocks,  such  as 
the  Archiean  and  PaleozcMC  series,  probably  because  heat 
and  metamorphic  action  are  commoner  in  these  older  rocks 
which  have  felt  all  the  throes  of  the  earth  from  past  to 
present  times,  than  in  the  more  recent  ones,  and  such  cir- 
cumstances, as  we  have  stated,  are  peculiarly  favorable  to 
vein  formation  and  mineral  deposition. 

The  bulk  of  our  precious  minerals  in  Colorado  comes  from 
the  older  Archaean  and  Paleozoic -series  of  rocks,  the  ex- 
ception being  the  Gunnison  region  around  Crested  Butte, 
Irwin  and  Ruby,  where  ore  comes  from  fissure  veins  in  the 
Mesozoic  Cretaceous  rocks.  The  exception  is  accounted 
for  by  the  local  metamorphism,  heat  and  eruptive  phe- 
nomena of  that  region. 


97 

The  veins  in  the  San  Juan  ha\'e  also  been  ascnboH  by 
sninc  to  the  Tertiary  Period,  owiiij^'  to  their  occurrenct-  in 
certain  supposed  Tertiary  la\'as  co  ering  that  district. 

Besides  heat,  nietamorphisin,  dynamical  disturbances  .;nd 
eruptive  agencies,  other  minor  circumstances  may  fa\-or  ore 
deptjsition.  Certain  rocks,  suclias  hmestones,  mayolTe:.  by 
their  tendency  to  sohibihty  and  chemical  reactions,  more 
fa\orable  conditions  than  others  lor  mineral  solutions  to 
ieposit  by  "  metasomatic  "  interchange  between  mineral 
ard  limestone,  until  the  limestone  is  gradually  replaced  by 
ore,  much  in  the  same  way  as  the  elements  of  a  water-logged 
trunk  of  a  tree  are  replaced  by  silica  in  the  process  of  fos- 
silizati(jn. 

CHANGE   OF    MINERALS   WITH    DEPIH. 

Lodes  often  change  in  the  character  of  their  PMuerals 
with  depth.  n(H  only  after  they  have  left  the  zone  l*  sec- 
ondary decomposition  and  surface  action,  but  also  far  below 
it.  Thus,  in  the  San  Juan,  some  of  the  mines  abound  in 
zinc-blende  near  the  surface,  which  with  depth  almost  dis- 
appears, giving  place  to  grav  copper  and  other  superior 
ores.  In  Cornwall,  England,  the  shallow  workings  yield 
copper,  and  with  depth,  tin  ;  and  hjcally,  many  such  changes 
may  characterize  a  particular  district  but  cannot  be  formu- 
lated as  a  rule  for  other  localities. 


INFLUENCE   OF   COUNTRY    ROCK. 

In  most  mining  regions,  to  which  Colorado  is  no  excep- 
tion, a  relation  has  been  observed  between  varieties  of 
'■  country  rock  "  and  ore  deftosits.  Veins  in  passing  from 
one  country  rock  to  another  are  liable  to  change  in  the  size 
or  variety  of  the  ore,  widening  in  connection  with  some 
rcKks.  and  pinching  or  growing  narrower  in  connecti<jn 
with  others. 

Certain  rocks  are  notorious  ore-bearers,  whilst  others  are 
notoriously  barren  over  large  regions,  or  in  special  locali- 
ties. 

The  presence  of  certain  rocks  adjacent  to  other  different 
rocks  nas  an  enriching  tendency  on  the  ore  bodies. 

As  regards  rocks  that  are  good  ore-carriers  or  receptacles 
of  particular  classes  of  ore  in  Colorado,  we  may  say  :  That 
quartzites  and  silicious  rocks  generally  carry  more  pyrites, 
and  are  gold-bearing. 

That  veins  in  granitic   rocks   carry   a   greater   variety   of 


9« 
inineials  than  others,  and  may  be  both  j<old  and  silver  bear- 

That  certain  limestones  carry  much  argentiferous  jralena. 

That  sandstones  and  other  unaltered  rocks  carry  little 
■ore  of  any  kind. 

The  influence  of  country  rock  on  veins  may  be  from  sev- 
eral different  causes,  for  instance  : 

Certain  rocks  are  by  their  structure  better  adapted  than 
others  for  forminjj;  rejj^ular  fissures.  Thus,  massive  lime- 
stone is  better  fissured  than  slate  i)r  shale,  leavinp^  wider 
open  spaces  fcir  the  ore  to  collect  in. 

Other  rocks  may  be  uK^re  porous,  and  admit  mineral  so- 
lutions through  their  pores.  Of  such  a  kind  are  s«jme  of  our 
p(jrphyries,  andesites  and  phonolites. 

Others,  like  limestone,  are  easily  acted  upon  by  solutions 
dissolving  (jut  the  rock  and  replacing  it  with  mineral  by 
substitution. 

Some  are  better  conductors  of  heat,  and  therefore  would 
assist  chemical  action  and  mineral  solution. 

And  lastly,  if  modern  theories  of  "  lateral  secretion  "  be 
true,  \iz.:  That  most  ore  comes  from  the  adjacent  country 
rock  and  is  precipitated,  substituted,  or  collected  in  the  vein 
fissure,  and  further,  that  the  metals  themselves  are  derived 
fn^rn  certain  metallic  elements  in  the  ordinary  constituent 
minerals  of  the  country  rock,  such  as  mica,  hornblende,  or 
augite.  it  is  clear  that  a  rock  composed  largely  of  such  min- 
erals would  be  liable  t(j  influence  the  vein  as  an  ore  gener- 
ator. Granite,  porphyries  and  andesites  are  largely  com- 
posed of  these  minerals. 

The  frequent  presence  of  eruptive  porphyry  rocks  near 
veins  and  ore  deposits  in  Colorado  shows  that  they  have  an 
important  influence  on  those  deposits,  which  may  be  of  va- 
rious kinds. 

F'irst,  that  in  their  component  minerals  and  mass  they 
actually  contain  the  elements  of  the  precious  metals  sub- 
sequently deposited  in  another  form  in  the  fissure  vein  or 
in  the  soluble  limestone  in  contact  with  it. 

Second,  by  the  heat  which  they  retain  for  a  long  time 
after  they  have  congealed  and  hardened,  they  would  assist 
in  the  reactions  of  any  chemical  or  mineral  solutions  that 
might  be  on  hand.  Lava,  at  the  time  of  its  erupti(jn,  is  al- 
ways highly  charged  with  steam  and  other  gases.  By 
reason,  also,  of  the  chemical  composition  of  porphyry, 
waters  p;'ssing  through  it  would  be  alkaline  and  assist  in 
dissolving  silica  and  t)ther  gangue  or  \'einstone  matter,  and 


99 


when  the  porphyry  has  thoroujjrhly  cooled  it  is  exceeflin>rly 
porous,  aiul  beinj^  much  j<<intcfl  and  cross-fractured,  be- 
comes Hke  a  /j^reat  spon{?e  tor  the  absorption  of  all  surface 
waters.  This  may  be  noticed  at  Aspen,  where  all  the  mines 
that  are  at  present  penetratinjjf  throujj^h  the  "  [lorphyry  cap" 
are  much  troubled  with  water,  far  more  so  tlian  in  the 
imderlyinjj;  limestone.  Surface  waters,  then,  becoming 
alkaline  by  passing  through  this  rock,  and  also  more  or  less 
iharged  with  carbonic  acid,  chlorine,  and  other  solvents, 
woulfl  be  ready  to  dissoh'e  both  gangui;  and  xein  ingredients 
out  of  the  i)orphyry  and  redeposit  tiiem  in  the  vein  fissure, 
or.  bv  metasomatic  substitution,  in  the  limestone  usually 
beneath  it. 

Water  circulating  in  fissures,  clianges  or  dissolves  the 
ingredients  of  the  surrounding  rock.  The  rocks  enclosing 
lodes  are  always  so  altered,  and  this  decomn(,sition  and 
alteration  is  not  alw;'.\s  merely  local  or  c<Hifinecl  to  the  close 
proximity  of  the  ore  hody,  but  we  often  finrl  a  whole  mining 
district,  such  as  Leadville,  Aspen  and  San  Juan,  pervaded  bv 
this  feature.  So  much  is  this  the  case  tliat  it  is  often  difficuft 
to  get  a  fresh,  unaltered  specimen  of  porphyry  or  some 
other  country  rock  within  the  district. 

The  brilliant  red,  yellow  and  maroon  tints  that  color  so 
much  of  the  mining  district  of  San  Juan  result  fnjm  the 
oxidation  of  pyrites  and  other  iron-bearing  minerals  per- 
vading the  eruptive  rocks,  and  it  is  noticeable  that  this 
color,  resulting  from  alteration  and  decomposition,  is  most 
prominent  in  those  parts  where  lodes  have  been  discovered, 
as,  for  example,  the  gorgeous  tints  of  the  Red  Mountain 
area  around  the  celebrated  "  National  Belle,"  "  Yankee  C^irl," 
and  I  ronton  mines,  between  Silverton  and  Ouray.  The 
rocks  in  Geneva  Gulch,  Hall's  Valley,  Buckskin  Canyon, 
and  in  other  mining  centers,  display  'Ve  same  beautiful  tints 
of  oxidation  in  the  vicinity  of  the  i:iiit«s. 

"  In  lodes  a  mutual  exchange  ta.-:.is  place  through  the 
reaction  of  the  ingredients  of  the  rock  and  the  materials  of 
the  vein.  Thus,  when  water  containing  carbonates  conies 
in  contact  with  rocks  c  minerals  containing  alkalies,  a 
chemical  reaction  takes  ;)lace.  When  these  last  are  com- 
bined with  silicic  acid,  these  silicates  are  decomposed  by  the 
carbonic  acid  and  the  bicail-'onates.  This  explains  both  the 
crystallizing  out  of  the  carbonates  and  the  so  frequent 
decomposition  of  rocks  containing  lodes,  especially  those 
which,  like  our  veins  in  granite,  are  feldspathic." 

The  same  principle  applies  to  other  ores  and  minerals  ir» 


'II 


lOO 


lodes.  Thus  the  precious  metals,  in  the  mines  of  Leadville 
in  their  original  condition,  have  been  proved  by  depth  to 
have  been  in  a  sulphide  state,  such  as  iron  pyrites  (sulphide 
of  iron),  or  galena  (sulphide  of  lead,  etc.).  Surface  waters 
charged  with  carbonic  and  other  acids,  passing  through  the 
overlying  porous  alkaline  porphyry  and  entering  the  under- 
lying limestones,  ha\'e,  as  we  have  previously  observed, 
changeo  the  sulphides  into  sulphates,  oxides  and'  car- 
bonates. 

The  presence  of  a  dyke  near  to  or  cutting  a  vein  has  been 
found  often  to  enrich  the  latter  at  the  p(jint  of  contact. 

In  the  "  Colorado  Central  "  mine  at  Georgetown  a  narrow 
dyke  of  brown  obsidian  traverses  a  large  dyke  of  ore-bear- 
ing porphyry.  The  valuable  ore  is  found  close  to  the 
obsidian  dyke.  Th's  might  be  the  result  of  greater  heat  at 
that  point.  The  "black  dyke  "  in  the  Comstock  mine  is  a 
somewhat  similar  case. 


PREJUDICE  IN  FAVOR  OF  AND  AGAINST  CERTAIN  ROCK.S. 

There  is  often  a  prejudice  lunongst  miners  in  favor  of 
certain  rocks  and  formations,  and  against  others.  Miners 
who  have  worked  perhaps  in  the  great  Comstock  mine  of 
Nevada,  or  the  Leadville  mines  of  Colorado,  or  the  fissure 
veins  in  granite  of  Jie  Old  World,  are  apt  to  look  out  for 
and  favor  certain  rocks  and  formalions  they  find  like  those 
they  have  been  accustomed  to.  Thus,  as  Mr.  Williams  says, 
"The  peculiar  'porphyry'  of  the  Comstock  was  hunted  up 
in  other  districts,  but  did  not  prove  metalliferous.  Solid 
granite  was  looked  upon  b}'  others  as  unfavorable,  gener- 
ally, because  localh^  some  granite  above  the  gold  belt  of 
California  had  proved  barren.  Yet  some  of  our  best  \'eins 
are  in  granite. 

"  Limestone  was  at  one  time  a  very  unpopular  rock  and 
supposed  only  locally  to  produce  lead,  till  the  discoveries  of 
Leadville,  and  Eureka,  Nevada,  overturned  the  scale  in  its 
favor." 

In  the  Leadville  "excitement  "  not  only  was  the  particular 
Carboniferous  limestone  of  Leadville  hunted  for  and  pros- 
pected, but  every  other  limestone  in  the  South  Park  region, 
no  matter  what  its  geological  age  or  position,  was  exten- 
sively prospected  without  results,  miners  not  recognizing 
the  fact  that  it  was  not  limestone  generally  that  produces 
rich  ores,  but  "a  particular  limestone  of  a  particular  geologi- 
cal period  (the  Lower  Carboniferous)  not  over  200  feet  thick, 


lOI 


0 


that  happened  locally  to  be  rich  near  Leadville,  and  the 
reason  of  its  being  locally  rich  at  that  point  was  owing  to 
the  concentration  of  eruptive  energy  at  that  point  ^.r.u  the 
intrusion  of  an  unusual  amount  of  porphyries,  which  in 
oint  of  fact  are  far  more  responsi'^Ie  for  the  ore  than  the 
imestone,  which  happens  to  be  merely  the  receptacle. 

It  was  also  quite  common  after  the  Leadville  excitement 
to  find  shafts  in  all  sorts  of  improbable  and  hopeless 
localities  whr)se  owners  wc^uld  tell  you  :  "  At  Leadville  it 
didn't  matter  where  a  man  'went  down.'  It  was  all  luck 
Avhether  you  'struck  it'  or  not,  and  so  they  night  as  well 
'go  down'  where  they  were  as  elsewhere."  It  was  often 
said  "that  Leadville  had  exploded  all  so-called  scientific 
theories  about  ore  being  in  one  fcnniation  or  locality  more 
than  another.     It  was  all  a  case  of  luck." 

The  excuse  for  tnis  is  to  be  found  in  the  fact  that  in  the 
immediate  vicinity  of  Leadville  it  did  scarcely  matter  "where 
vou  went  down,"  seeing  that  that  area  was  practically  under- 
laid by  bedded  sheets  of  mineral,  but  that  such  would  be  the 
case  elsewhere  and  everywhere  or  anywhere,  experience 
unfortunately  has  shown  to  be  untrue.  It  is  not  a  pa»*- 
ticular  rock  or  formation,  but  a  combination  of  favorable 
circumstances  that  alone  can  make  a  rich  mining  district. 

As  experience  advances,  geologists  and  miners  have 
proved  that  ore  deposits  have  a  much  wider  range  vhan  was 
once  supposed.  Formerly  only  the  Archaean  granite  series 
was  supposed  capable  of  bearing  ore  deposits,  because  in  the 
Old  World,  tin,  copper  and  lead  came  principally  from  fissure 
veins  in  those  rocks.  Then  deposits  were  found  in  the 
Paleozoic  series  and  supposed  to  ascend  no  higher.  But  in 
the  present  day,  and  even  in  Colorado,  they  are  traceable 
even  to  the  Tertiar\;. 

It  is  not  the  rock,  nor  the  age,  but  a  combination  of  cir- 
cumstances, principally  heat  and  metamorphism,  that  may 
make  any  rock  of  any  period  an  ore-bearing  one.  And  in 
prospecting  in  new  regions  it  is  these  comlainations  rather 
than  any  particular  rock  that  should  be  looked  for. 


STRIKE   AND    DIP   OF   VEINS. 


The  dip  of  veins  approaches  more  nearly  the  vertical  than 
the  horizontal,  usually  from  75°  to  verticality.  Nearly  all  our 
ore  deposits,  in  Colorado,  even  those  of  trie  bedded  class, 
dip  more  or  less  steeply  from  25°  to  75°. 

For  a  few  feet  from  the  surface,  on  the  steep  slope  of  a 


I02 


mountain,  it  is  common  to  find  an  ore  deposit  dipping*-  quite 
gently  or  even  folded  over  and  dipping  in  a  contrary- 
direction  to  that  which  it  assumes  with  clepth.  This  appears 
to  arise  from  the  weight  of  the  strata  above  it  tending  to 
bend  it  over  downward  in  the  direction  of  the  slope  of  the 
hill. 

There  is  generally  a  prevailing  dip  and  strike  amongst  a 
number  of  parallel  fissure  veins  of  a  district.     In  the  San 

Juan,  the  bulk  of  the  fis- 
sure veins  have  a  prevail- 
ing northeasterly  strike 
and  dip  to  the  southeast. 
The  angle  of  dip  is  gen- 
erally between  60'  and 
verticality. 

CROSS-CUTTING   UN'CF.R- 
TAIX. 


The  dip  as  we  have 
said,  not  unfrequcntly 
changes  considerably 
with  depth,  usually  be- 
coming more  and  more 
vertical.  From  the  de- 
gree of  uncertainty  as  to 
the  continuit}'^  of  the  dip, 
it  is  not  always  safe,  on 
the  discovery  of  an  outcrop,  to  endeavor  to  cut  it  at  a  much 
lower  point,  so  as  to  get  the  coveted  depth,  and  better 
opportunities  for  stophig,  drainage  and  other  developments 
of  the  riine.  Owing  to  a  change  of  dip  or  fault,  perhaps, 
thv.  miner  ma}-  have  to  make  a  much  longer  cross-cut  tunnel 
than  he  had  calculated  upon  before  striking  the  v^ein. 
Sometimes,  too,  he  may  miss  the  vein  altogether,  cutting  it 
perhaps  at  some  point  where  it  is  exceedingly  thin  or  poor, 
so  poor  in  fact  that  he  passes  through  it  without  noticing  it 
or  believing  it  to  be  the  same  vein  whose  outcrop  looked  so 
promising  on  the  surface.  Cross  tunnels  through  "dead 
rock  "  should  hardly  be  undertaken  until  the  vein  has  been 
proved  to  be  a  strong  one  for  a  considerable  depth.  As  we 
have  already  shown,  graat  deptns  may  not  after  all  be  so 
desiiable  in  even  a  fissure  vein,  as  there  is  no  certainty' 
whatever  about  veins  becoming  richer  or  poorer  with  depth. 
Extensive  cross-cut  tunnels  have  seldom  proved  paying 
concerns.     The  greatest   in  the   United  States,  the   Sutro 


Plate  LXII. 

Showing  How  Cross-cut  Tunnels  and  Shafts 
May  Miss  Veins  by  Change  of  Dip  or 
Faulting. 


I03 


tunnel,  six  miles  in  length,  which  tapped  the  Comstock 
fissure  at  a  depth  of  2,000  feet,  did  not  prove  a  financial 
success,  and  had  it  tapped  the  fissure  still  lower,  at  3,000 
feet,  it  would  have  found  the  vein  in  the  impoverished  con- 
dition it  is  to-day.  It  is  not  unco'Timon  for  a  miner  to  strike 
a  rich  outcrop  on  the  top  of  some  mountain,  and  on  the 
strength  of  its  richness  induce  a  company  to  run  a  long 
cross-cut  tunnel  in  "dead  rock"  half  through  the  mountain 
to  cut  this  vein,  and  the  company's  resources  are  nearly 
exhausted  in  so  doing,  while  the  vein  itself  gives  no  returns, 
owing  to  its  being  left  idle. 
Finally,  perhaps,  the  vein  is 
missed,  or  if  struck,  proves 
far  poorer  than  was  antici- 
pated. Of  course  there  are 
exceptions  where  cross-cut 
tunnels  in  "  dead  ock  "  may 
be  advisable. 

If  a  fissure  vein,  as  in  the 
San  Juan,  should  outcrop 
near  the  top  of  a  mountain 
and  be  exposed  on  its  dip 
all  the  way  to  the  bottom, 
there  may  be  some  reason 
for  opening  a  tunnel  in  it 
near  the  base,  thereby 
facilitating  drainage,  de- 
velopment and  exportation. 

In  that  case  the  miner  is  on  the  vein,  with  no  fear  of  losing 
it ;  but  even  here,  there  is  no  guarantee  that  it  will  prove 
rich  all  the  way  to  its  outcrop  a  thousand  feet  above.  *'  Fol- 
low your  ore,  and  be  careful  how  you  leave  it  for  any  ex- 
perimental theories,"  is  a  common  and  wise  saying  among 
experienced  miners.  We  remember  a  tunnel  in  the  Gun- 
nison region  which  was  run  several  hundred  feet  at  a  cost 
■of  many  thousands  of  dollars,  all  through  "dead  rock.'' in 
the  hopes  of  cross-cutting  a  certain  ore  body  that  had 
proved  rich  near  the  surface.  At  last  it  was  given  up,  and 
subsequently  a  short  cross-cut  was  made  from  it,  and  the 
original  vein  was  found  only  a  few  feet  from  the  tunnel, 
which  had  been  running  parallel  with  it  all  the  time.  The 
<:ause  of  the  mistakt  was  an  unforeseen  fault  in  the  vein  that 
had  shifted  its  dip  much  further  on  one  side  than  had  been 
calculated  upon. 


uts 


Plate  LXIII. 

Fissure  Vein  Exposed   From  Outcrop  to 
Dip. 


104 

CHAPTER  IX. 
GOLD    PLACERS 

PROSPECTING    FOR   PLACER   GOLD   AND   GOLD    VEINS. 

Having  given  in  preceding  chapters  a  sketch  of  veins  and 
ore  deposits  in  the  rocks,  it  follows  in  order  to  speak  of  gold 
placers,  because  these  are  derived  from  the  former  by  the 
agencies  of  water,  either  in  the  form  of  glaciers  of  old,  or  of 
ancient  or  modern  streams. 

The  glaciers  in  olden  times  heavilj''  mined  the  r6cks  and 
the   veins,   by  cutting   broad  gashes   through    then.,   thus 

originating  the  can- 
y(3ns.  In  this  way 
millions  of  tons  of 
rock  were  mined,  to- 
gether with  the  gold- 
bearing 


Plate  LXIV. 

Open  Placer  Grounds  in  Canyon. 


veins  in 
them,  and  also  the 
precious  metals  mi- 
nutely diffused  and 
scattered  through- 
out their  masses. 

After  the  glaciers, 
the  rivers  took  up 
the  work,  deepened 
the  canyons,  broke 
up  the  boulders  and  sorted  them,  setting  free  the  gold  and 
other  metals  they  contained,  and  again  sifted  and  sorted 
them  and  deposited  them  along  their  banks  and  in  their 
beds. 

Of  the  vaiious  metals  thus  handled  by  nature's  jigging 
process,  many  were  dissolved  and  destroyed  b)^  various 
acids  in  the  waters,  and  by  acids  of  vegetation  and  iron  salts 
percolating  through  the  placer  dumps  after  they  had  been 
laid  down.  So  with  the  exception  of  a  few  ver}"  hard 
minerals,  such  as  magnetite,  diamonds,  garnets,  rubies,  etc., 
little  remained  in  the  placer  but  the  imperishable  gold,  and 
even  that  appears  to  have  been  refined  of  its  alloy  of  silver 
which  it  contained  in  the  original  vein,  for  placer  gold  is 
generally  much  purer  and  more  valuable  than  that  in  the 
original  vein. 
In  some  cases,  too,  the  fine  gold  disseminated  through 


I05 


the  placer  appears  to  have  been  acted  upon  by  certain  silts, 
such  as  the  persalts  of  iron,  and  concentrated  and  amalga- 
mated into  large  nuggets.  Some  contend,  however,  that 
these  nuggets  are  only  waterworn  pebbles  of  gold,  brought 
direct  from  the  vein,  the  result  perhaps  of  concentration 
there  of  the  contents  of  large  masses  of  gold-bearing  pyrites  ; 
it  is  to  be  noted,  however,  that  whilst  gold-bearing  nuggets 
of  various  sizes  are  to  be  found,  not  uncommonly  in  gold 
placers,  they  are  very  rarely  found  in  gold  veins. 

With  the  gold  in  placers,  is  commonly  found  what  is 
called  "  black  sand,"  which  is  composed  of  grains  or  pebbles 
of  magnetic  iron  ore,  relics  of  the  old  gold-bearing  pyrites 
chemically  changed.  Being  near  in  gravity  to  gold,  and 
originally  associated  with  it,  the  two  are  generally  found 


S/6.N.D  SOLQ^ 


Plate  LXV. 

Section  in  Gold  Placer, 

together  in  a  placer,  and  a  prospector  in  surv^eying  a  bank 
of  placer-material  made  up  of  sand,  pebbles  and  boulders, 
generally  looks  for  a  streak  of  "black  sand"  as  a  likely 
place  for  gold.  Also  by  reason  of  the  gravity  of  gold  he  is 
inclined  to  look  for  it  more  down  on  bed-rock  than  in  the 
upper  looser  strata. 

Ancient  river  beds  as  well  as  those  of  modern  riv^ers  may 
be  found  gold-bearing,  rivers  that  have  long  ceased  to  flow, 
by  reason  perhaps  of  change  in  the  configuration  of  the 
country.  In  California  and  Australia  many  of  these  ancient 
gold-bearing  river-beds  have  at  a  period  not  long  distant, 
been  deluged  and  covered  by  lava,  and  the  gold  is  extracted 
by  tunnelling  beneath  the  lava-sheet  or  by  shafting  down 
through  it  to  the  gravel  below.  These  are  called  deep  leads 
whilst  the  ordinary  uncovered  gravels  are  called  "  shallow 
placers." 


io6 


i\  i 


! 


Almost  anywhere  along  ancient  or  modern  water  courses 
not  far  from  mountains,  a  prospector  by  panning,  can  get 
colors  of  gold  even  on  the  pebbly  "  wash  "  covering  the 
surfaces  of  large  portions  of  our  plains,  or  even  on  the  tops 
of  table  lands  that  once  were  plains,  over  which  broad  rivers 
and  glaciers  and  large  bodies  of  water  distributed  their 
debris,  but  as  a  rule  it  will  only  pay  to  work  where  the 
"wash"  or  "drift"  or  "alluvial"  matter  is  plentiful  and 
thick,  and  more  than  this,  only  where  water  is  accessible  to 
the  work. 

PROSPECTING. 

A  prospector  hunting  for  a  gold  placer  follows  up  the 
water  channels  in  which  he  finds  specimens  of  all  the  rocks 
in  the  neighborhood.  Tn  Australia,  the  prospector  h^oks 
amongst  these  to  find  samples  of  granitic,  porphyritic  and 
quartzose  rocks  or  clay-s!ate  as  likely  signs,  and  also  pieces 
of  quartz  honey-combed  and  rust)',  which  we  have  described 
before  as  "  float  or  blossom."  Plenty  of  broken  up  quartz 
he  considers  a  good  sign,  but  very  pure,  hard,  dull  white 
quartz  is  generally  considered  as  "hungry"  or  "  barren  ;"^ 
the  size  of  the  fragments  denotes  his  nearness  or  otherwise 
to  the  reef,  z.  e.,  the  vein. 

A  prospector  examines  closely  the  fine  sandy  matter  of 
the  stream  bed  especially  where  eddies  and  backwater  have 
been  formed.  A  likely  deposit  should  be  scraped  up,  even 
down  into  every  crevice  and  depression  in  the  bed  rock  or 
solid  rock  bottom  over  which  the  river,  modern  or  ancient, 
has  worn  its  channel.  This  material  should  be  panned. 
Gold,  too,  is  often  found  on  points  and  slopes  of  the  bed  rock 
as  well  as  in  the  deepest  portion.  Nuggets  found  on  high 
reefs  above  the  level  of  the  stream,  imply  that  their  weight 
enabled  them  to  remain  in  their  position,  during  the  deeper 
erosion  of  the  neighboring  streams,  and  that  the  original 
vein  from  which  they  came,  is  not  far  off.  As  a  rule,  large 
nuggets  and  coarse  gold  are  found  much  nearer  to  the 
source  whence  they  came,  than  fine  or  "  flour  "  gold,  which  is 
often  carried  to  unlimited  distances  away  out  on  the  plains. 

The  character  of  quartz  veins  and  of  their  emclosing^ 
rocks  in  the  immediate  vicinity,  decides  the  character,  too, 
of  gravels  derived  from  them,  hence  sometimes  a  peculiar 
pebble  may  be  traced  up  to  the  peculiar  rock  Avhence  it 
came,  and  the  gold  vein  be  found  near  it  in  place. 

It  has  been  observed  that  "  leads  ''following  the  course  or 
lines   of  a  gold-bearing  reef,  maintain  a  more  continuous 


loy 


yield  than  those  crosstfig  a  number  of  gold  reefs  at  intervals, 
i^old  occurs  in  pockets  and  "  shoots  "  at  intervals,  with 
barren  portions  between,  which  accounts  for  what  we  have 
stated  above.  In  a  country  where  the  gold  quartz  veins  are 
small,  though  rich  at  wide  intervals,  the  gravels  will  also  be 
small. 

In  very  deep  ground  where  the  "wash  "  is  very  heavy  a 
series  of  borings  or  even  shafts  are  made  to  test  the  quality 
of  the  bank.  The  following  points  have  been  observed  as 
worthy  of  note  in  prospecting  for  gold  placers. 

I.  Streams  crossing  the  lamina  or  stratification  planes  of 
gold  reefs  at  right  angles  are  likely  to  be  richest. 


Plate  LXVI. 

Shallow  Placer— Gold  Sand  in  Potholes  A,  A  and  Below  a  Hard 

"Bar"  B. 

2.  Gold  is  rarely  found  jjlentiful  where  there  are  indica- 
tions that  the  current  was  strong,  but  rather  in  the  lee  under 
projecting  points  of  rock,  where  beaches  are  usually  formed 
and  the  water  was  slack. 

3.  Gold  in  streams  is  deposited  in  crevices  of  the  "bed 
rock,"  which  should  be  laid  as  dry  as  possible  and  picked 
up  to  such  depths  as  the  sand  descends  between  the  lamina- 
tions. 

4.  Terraces  are  shelf-like  excavations  and  deposits  upon 
hill  slopes  above  valleys,  and  are  the  remains  of  old  glacier 
or  river  beds.  The  prospector  should  discover  the  inlet  and 
outlet  of  the  terrace  and  examine  the  gravel.  The  "wash  " 
sometimes  contains  gold  in  layers  one  above  the  other. 

5.  Whilst  working  up  stream  attention  should  be  paid  to 
the  banks  on  each  side  where  sections  are  exposed  so  that 
no  outcropping  vein  be  overlooked. 

6.  Alluvial  gold  should  if  possible  be  traced  to  its  source 


io8 


whence  the  "  float  "  came.  When  the  pold  is  large  and 
plentiful  and  the  boulders  large  and  angular  the  reef  is 
likely  not  far  distant. 

7.  'Sometimes  there  is  a  dist.nct  peculiar  feature  in  all  the 
veins  of  a  district,  such  as  a  peculiar  band  of  a  definite  color. 

8.  Coarse  alluvial  gold  is  not  always  incompatible  with  fine 
reef  gold  as  a  source,  because  the  reef  gold  may  be  so  tine  in 


Platk  LXVII. 

Shallow  Placer— flold  Sand  Behind  Bar  on  One  Side  of  Creek. 

general  as  to  lend  itself  to  very  wide  distribution  when  once 
it  is  liberated,  while  the  rarer  coarse  grains  would  not  be 
transported  far. 

9.  Alluvial  placers  are  richest  where  the  current  of  the 
stream  is  interrupted  by  diminution  in  fall,  by  sudden 
change  of  direction,  or  by  entrance  of  a  tributary,  also  by 
reefs,  bars,  eddies,  etc.  Absolute  richness  depends  upon 
local  circumstances  and  the  size  and  weight  of  floated 
masses. 

10.  Creases,  holes  and  fissures  of  bed-rock  over  which  the 
stream  passed  are  favorite  places. 

11.  The  lowest  layers  of  each  separate  period  of  deposition 
are  the  richest.* 

Sometimes  several  different  periods  of  deposition  have 
succeeded  each  other. 

12.  The  courses  of  present  streams  and  of  ancient  chan- 
nels are  placers. 

"Loaming"  is  a  form  of  prospecting.  It  is  preliminary  to 
such  prospecting  as  cutting  experimental  trenches,  or  sink- 
ing trial  shafts  or  boring.  It  consists  in  washing  surface 
prospects  from  the  bases  and  slopes  of  the  ranges,  until 
specks  of  gold,  or  specimens  are  found  to  be  obtainable 
with  tolerable  frequency,  within  certain  limits.  The  pros- 
pector then  proceeds  to  trace  the  gold  up  hill  to  its  source. 


I09 


narrowing  the  limits  of  his  work  as  by  patient  search  ht' 
approaches  the  vein,  whence  the  gold  has  been  derived.. 
Wlien  he  can  obtain  surface  prospects  of  gold  uji  to  a  certain 
point,  or  line,  but  no  farther,  he  then  prcjcecds  bj'  means  of 
trenching  to  search  for  the  gold  vein.  The  prospector  has 
often  to  work  along  a  steep  scrubby  mountain  side  selecting 
his  prospects,  numbering  them,  and  placing  samples  in  hi.> 
"loam  bag."  If  he  discovers  prospects  f)f  gold,  he  finds  his 
w^ay  back  to  the  spots  the  samples  were  taken  f"'om,  so  as  to 
continue  his  up-hill  search,  and  trace  the  gf)ld  to  its  source 
or  vein.  Sometimes  there  is  no  indication  of  a  vein,  soil 
and  bushes  and  debris  cov^ering  its  out-crop,  but  by  loaming, 
the  prospector  ascertains  its  position,  so  as  to  expose  it  by 
a  trench  not  many  feet  in  length. 

We  remember  an  ingenious  way  in  which  a  valuable  and 
long  sought  f(jr  vein  was  at  last  discovered.  Prcjspectors 
had  long  found  very  rich  "float"  at  the  base  of  a  hill 
whose  surface  was  so  deeply  covered  with  loose  debris 
that  no  trace  of  the  vein  could  be  fcnind.  A  prospector 
found  a  small  lake  on  top  of  this  hill,  and  conceix'ed  the 
idea  of  cutting  a  trench  from  this  body  of  water  to  the 
edge  of  the  hill,  and  by  damming  up  the  trench,  and  then 
suddenly  letting  out  the  water  to  full  force,  it  cut  a 
deep  trench  through  the  loose  debris  down  to  bed  rock 
and  the  vein  was  discovered.  This  process  is  called  "  boom- 
ing." 

The  cleavage  of  quartz  is  said  to  be  freer,  sharper  and  bet- 
ter defined,  in  gold-bearing  quartz  than  in  that  which  is  bar- 
ren. Pj'^rite  is  a  good  indication.  A  soft,  fatty  clay  or  gouge 
often  flanks  the  vein  in  its  gold-bearing  portions. 

The  mountain  spurs  should  first  receive  attention  for 
veins;  if  the  quartz  is  hard,  it  stands  up,  if  soft,  as  it  more 
commonly  is,  it  will  leave  a  streak-like  depression.  On  find- 
ing such,  the  prospector  should  first  wash  out  some  of  the 
decaying  rock.  If  only  a  trace  of  gold  is  found  in  the  quartz, 
there  is  probably  a  gold  vein  in  the  neighLoihood,  and 
trenches  should  be  dug  and  exploration  systematically  fol- 
lowed up.  Gold  is  generally  near  one  wall  of  a  vein,  seldom 
all  through  the  stone.  Quartz  gold  occurs  in  "shoots" 
with  barren  spaces. 

Before  setting  a  valuation  on  a  discovery,  the  facilities  for 
working  the  mine,  such  as  we  have  alluded  to,  should  be 
considered.  Placer  mines  as  well  as  other  mines  are  often 
supposed  to  be  "  worked  out."  These  are  sometimes  well 
worth  investigating  and  examining  by  cross-cuts  or  other 


I  lO 


means.  S(jmctiines  it  happens  tliat  more  ^<>\<\  is  obtained 
from  "  leafier"  veins  that  nad  been  overlooked,  than  from 
the  main  worked  vein. 

(Jnite  C(jmmonly.  especially  in  the  lower  part  of  a  placer, 
the  pebbles  and  sand  are  firmly  cemented  tof.fether  int<j  a 
coarse  conglomerate  by  infiltration  of  iron  oxide  and  clay. 
This  may  consolidate  into  a  false-bottom  and  niH  be  true 
"  bed  rock."  (icnerally  two  or  three  such  false-bottoms, 
with  intervening,'-  strata  of  jj^reater  richness,  alternate  with 
barren  ones.  So,  many  old  di^f^inj^s,  thus  supposed  to  ha\e 
been  exhausted,  may  be  worked  ajj^ain,  the  true  bottinn  not 
having-  been  reached.     These  conglomerate  bottoms  may  lie 


just  upon  bed-njck,  with  a  white  clay  rich  in  gold  l)eneath 
them.  Gold  occurs  also  in  the  conglomerate  and  must  be 
stamped  (JUt. 

Modern  rivers  fretiuently  cross  in  their  course  old  river 
courses,  and  redistribute  their  golden  sands. 

Placers  are  richer  in  their  richer  parts,  than  the  \eins  from 
which  their  g<-)ld  was  derived. 

When  shallow  placers  are  due  to  the  wearing  down  of 
quartz  veins,  no  placer  will  be  found  abo\e  these  veins,  or 
above  the  point  where  the  vein  crosses  the  placer.  In  the 
Sierra  Nevada  there  is  but  little  alluvium,  the  gold  comes 
from  veins  near  by. 

Gold  placers  maj'  sometimes  occur  below  silver  mines. 
Thus. the  Comstock   vein  was  discovered   by  fcjUowing  up 

Elacer  gold  to  its  source.    This  vein  has  produced  a  gold- 
earing  silver-ore,  the  silver  rapidly  disappearing  and  lea\'- 
ing  the  gold  behind. 


EXAMPLE  OF  A    PLACER. 

In  Ballarat,  Australia,  the  "  wash-dirt  "  runs  in  a  series  of 
"  leads  "  of  varying  width,  starting  from  the  same  point,  and 
trending  in  difterent  directions  towards  the  "deep  leads." 
The  "  reef  wash  "  is  about  loo  feet  deep,  the  "pay  dirt"  5 
feet.  The  barren  drift  wash  overlying  the  "  pay  dirt  "  is  of 
black  clay.  The  reef  itself  is  of  green  slate,  the  bed-rock  is 
sandstone.  Gold  lies  sometimes  on  thin  layers  of  sand  or 
"  pipe  clay"  on  the  surface  of  the  "  bed-rock,"  more  often 
in  crevices  of  the  bed-rock  itself,  which  is  more  or  less 
rotten.  This  bed-rock  is  broken  up  for  some  12  to  20  inches 
and  the  gold  is  found  in  "pot-holes  "  in  it  15  to  18  inches  in 
diameter  and  6  to  10  inches  deep,  cut  out  of  the  solid  rock. 
The  alluvial  gold  is  found  chiefly  in  bed-rock  of  slate,  dip- 


1 1 1 


ping  90  degrees.  Some  of  these  slates  arc  soft  and  rotten, 
others  are  indurated.  On  the  soft  rock  only  is  the  gold 
found.  Nuggets  are  found  in  the  soft  clay  lying  on  "  bed- 
rock." Slate  forms  natural  "riHles"  for  catching  the 
gold. 

Deep  pools  under  waterfalls  in  gold-hearingstreams  rarely 
carry  much  gold.  So  in  rivers,  gold  is  found  in  "  bars"  or 
points  rather  than  in  deep  pools  or  bends. 


CHAPTER  X. 


"DEEP   LEADS." 

A  "  deep  lead  "  lies  deep  below  the  surface,  often  covered 
by  beds  of  lava,  especially  in  California.  These  lava  beds 
may  be  many  in  number,  and  hundreds  of  fevt  in  thickness. 
The  "deep  lead"  is  an  ancient  river  bed. 

In  the  Sierra  Nevada  the  gold  is  derived  from  meta- 
morphic  crystalline  rocks  of  the  range,  partly  from  quartz 
veins  in  the  slates,  and  partly  from  gold  distributed  in 
minute  quantities  all  through  the  metamorphic  rocks.  The 
quartz  veins  lie  between  the  planes  of  stratification  of  the 
slates,  also  in  irregular  bunches  and  lenticular  masses  of 
limited  extent.  In  many  localities,  the  rocks  are  penetrated 
in  every  direction  by  little  irregular  quartz  veinlets,  which 
often  carry  gold,  and  in  spots  are  extremely  rich,  even 
where  the  quartz  vein  is  only  an  inch  thick.  In  some  Cali- 
fornia districts,  wherever  a  basalt  capping  exists,  the  drift 
beneath  it  is  auriferous. 

In  California  the  modes  of  occurrence  of  auriferous  gravel 
deposits  are  various. 

"  Sometimes  they  exist  in  well-defined  ancient  river- 
beds under  a  capping  of  basalt  which  has  filled  the  channels 
of  the  rivers  in  past  ages.  Again,  they  appear  in  isolated 
mounds  or  hillocks,  evidently  the  remains  of  such  channels, 
which,  being  unprotected  by  a  covering  of  lava,  have  been 
broken  up  by  the  action  of  the  elements,  also  in  basins  or 
flats  which  have  received  the  wash  of  these  disintegrating 
rivers,  also  in  low,  rolling  hills  near  the  base  of  the  Sierras, 
and  beyond  the  reach  of  the  lava-flows."  One  of  the  most 
remarkable  and  important  gold  leads  is  that  beneath  Table 


UJ 


Mountain  in  Tuolumne  County.  "  The  waters  perrolatinjj^ 
throiiirli  these  hiva-llows  anrl  reachinj^f  the  j^ravels  beneath. 
are  cnarjifed  with  alkali  from  the  lava,  These  alkaline 
waters  are  charjj^ed  with  silica  in  solution  f'oin  the  same 
source.  Hence  the  fossil  drift-woocl  of  these  ancient  ri\ers 
nas  all  been  silicified  by  these  silicious  waters.  The  /^navels 
are  also  cemented  by  the  same  material.  These  percolating? 
waters  also  contained  iron,  for  iron  pyrites  is  found  in  con- 
tact with  the  silicified  woods.  In  this  ir<jn-cement.  >?old  is 
fcHind  in  rounded  pfrains  and  in  minute  crystals,  anrl  threads 
deposited  by  a  solution  of  sulphate  of  iron  .it  the  moment 
of  the  reductif)n  of  the  latter  to  a  sulphide." 


BABKLT 


Plate  LXVIII. 

Deep  Placer,  T.ible  Mountain,  Cal. — A  A,  Ancient  River  Channel,  with  (iold-hear- 
ing  Gravel ;  B  B,  Sandstones  and  Shales  with  Fossil  Bones  and  Silicified  Wood. 

The  dead  rivers  of  California  are  on  the  west  slopes  of  the 
Sierra  Nevada,  from  500  to  7000  feet  above  sea-level.  The 
largest  and  richest  lead  is  the  "  f^ig  Rlue  Lead"  traced  65 
miles  and  even  no  miles.  It  is  parallel  with  the  main 
divide  of  the  Sierra  Nevada.  The  live  modern  rivers  run  at 
right  angles  io  it,  cutting  canyons  1,500  to  3,000  feet  deep. 
The  "  Blue  Lead  "  runs  across  these  ridges  from  200  to  1000 
feet  below  their  summit.  The  lead  was  disc(jvered  by  fol- 
lowing up  surface  washings.  Miners  found  that  the  modern 
streams  were  richly  gold-bearing  up  to  a  certain  point,  in- 
creasing as  this  point  was  neared  but  ceasing  when  it  was 
passed.  These  parts  were  in  the  line  of  the  different  streajns, 
and  by  following  up  indications,  the  lead  was  eventually 
struck  on  several  sections  and  tunnelled  on.  The  deposit 
is  300  feet  deep,  composed  of  gravel,  boulders,  clay,  and 
sand,  on  strata  distinguished  by  degrees  of  fineness,  by  the 
character  of  the   rocks,   and   the   amount   of  gold,   also  by 


"3 

Colors,  the  prt.'\ailiii>;  lolor  bc-in^,'  a  bhic-jj^iay.  (»old  is 
Courser  near  the  bottom,  anri  contains  a  >j;reater  alloy  of 
silver.  The  silver  in  the  f/oiri  in  the  upper  strata,  has  been 
eaten  out  by  suiphuiDUs  acid  resultinj,'  troni  decomposition 
of  iron  pyrites.     The  whole  deposit  is  like  that  in  e.xisting 


ri\iis,  showiu)^'  banks,  bars,   cfldies,    falls,  rapids  and  rillles 


Tlu-re  is  nuu  li  ^okl  in  the  edtiics  and  but  liltfe  in  the  rapids. 
The  space  between  the  boukiers  is  tilled  with  sand  and  con- 
tains fjold,  the  bed-rock  is  slate. 

Where  dead-ri\ers  meet,  the  "wash"  is  j^enerally  rich. 
Where  a  lead  becomes  very  narrow,  dips  fast,  and  isinchjsed 
between  steep  walls,  the  ^old  will  be  \ery  sparingly  dis- 
tributed in  holes  and  behind  rid>j^es  anfl  will  be  coarse  in 
size. 

\'ery  larjj^e  and  abundant  boulders  in  j^old-bearinj^  stream 
beds  are  often  a  serious  obstacle  in  jj^ettinjj;^  out  the  j,^old, 
from  the  dilliculty  of  handling  them.  More  than  one  placer 
has  been  abandoned  from  this  cause  alone. 


HVDRAUMCS. 

Placer  banks  are  worked  on  a  larjj;e  scale  by  "Giant 
nozzles  "  or  Hydraulics.  Before  commencing  such  work 
the  total  depth  of  the  placer  deposit  should  be  examined 
anfl  ascertained,  and  the  richness  of  the  strata  th;.)Uj.>^hout 
tested.  Shafts  should  be  sunk  here  and  there  to  bed  rock 
for  this  purpose,  and  topographical  surveys  made  tt^  ascer- 
tain what  fall  and  head  of  water  can  be  obtained,  and 
what  outlet  also  for  the  tailings,  as  the  latter  would  soon 
choke  up  the  work;  the  ground  sometimes  may  be  too  flat 
to  dispose  of  the  tailings  by  stream-power.  The  choking 
of  outlets  is  a  fertile  source  of  abandoning  placers. 

Jh'iu/t  Mining. — "The  beach  sands  of  the  Pacific  and  else- 
where contain  minute  scales  of  gold  and  s(jmetinies  platinum, 
together  with  a  great  deal  of  magnetic  iron  ore.  Winds, 
tides,  and  surf  act  as  natural  concentrators  or  separators,  in 
parting  the  light  and  useless  material  from  tlie  heavier. 
Wind  drives  heavy  swells  on  the  beach  at  high  tide  to- 
gether with  sandy  matter.  At  ebb  ot  tide,  the  surf  lashes 
the  beach  and  carries  back  light  portions  of  the  mass  with 
the  undertow,  lea\'ing  some  iron  sand,  gold  and  platinum, 
whose  weight  enables  them  to  hold  their  place.  At  low 
water,  miners  go  down  on  the  beach,  scrape  up  the  iron 
sand,  which  is  generally  left  in  thin  layers,  stacking  it  back 
from  reach  of  the  surf,  and  subsequently  washing  out  the 


Kt; 


114 

gold."  In  some  beaches  much  of  this  sand  contains  titanif- 
erous  iron  ore  and  if  attempts  are  made  to  use  certain  pro- 
cesses to  save  the  finer  gold  the  character  of  the  iron  may 
be  a  formidable  obstacle. 

EXAMPLE   OF   COLORADO   PLACER  GOLD    MINES. 

California  gulch,  the  site  of  the  present  Leadville,  fur- 
nished a  great  amojnt  of  gold  in  the  early  days  till  the  dis- 
covery of  the  lead-silver  deposits  in  place.  This  discovery, 
also,  was  due  to  placer  mining.  Whilst  examining  the 
gravel  in  the  gulch,  Mr.  Wood,  an  intelligent  prospector,  was 
struck  by  the  appearance  of  what  the  miner*  railed  "  heavy 
rock"  some  of  which  he  assayed.  His  specimens  yielded 
27  percent,  lead  and  15  ounce's  silver  to  the  ton.  He  put 
prospectors  to  work  to  find  the  croppings  of  the  ore  de- 
posits, and  in  June,  1874,  the  first  "carbonates  in  place" 
were  found  on  Dome  Hill.  This  was  practically  the  beginning 
of  Leadville.  It  is  said  that  upwards  of  2,000,000  dollars 
worth  of  gold  was  taken  out  of  this  gulch  in  one  summer 
before  the  mines  in  place  were  discovered  or  opened  up. 

It  is  noticeable  that  California  gulch  alone  furnished 
almost  all  this  placer  gold,  whilst  Iowa  and  Evans  gulches 
adjoining  it  on  either  side,  and  carved  out  of  the  same  series 
of  rocks  yielded  little  or  nothing.  Why  should  the  smaller 
gulch  contain  exceptionally  rich  gravels  and  its  neighbors 
be  barren  ? 

The  richest  portions  of  California  gulch  were  found  at 
bends  in  the  course  of  the  gulch.  In  one  place  near  Oro 
in  the  narrow  bed  of  the  gulch,  a  gold-bearing  cement  was 
found  containing  hydrated  oxide  of  iron,  below  the  gravel, 
yielding  an  ounce  of  gold  to  the  ton.  The  gulch-gold  was 
worth  $19  per  ounce  whilst  that  froii  the  mines  in  place  only 
$15.  The  Printer  Boy  porphyry  containing  actual  gold  veins 
in  place  may  have  been  the  source  of  some  of  the  gold  in 
the  gravels,  together  with  the  oxide  of  iron  resulting  from 
the  decomposition  of  pyrites  in  the  pyritiferous  porphyry  as 
a  cen^.enting  material.  Also  the  "Weber-grit"  sandstones 
at  the  head  of  the  gulch  have  been  found  to  carry  small 
gold  veins,  and  from  their  abrasion  also  gold-bearing  gravels 
would  have  been  carried  down  the  gulch.  Also  of  late  the 
rich  gold  deposits  of  Breece  Hill  at  the  Ibex  and  Little 
Johnnie  mines  have  been  found. 

"  It  is  doubtful,"  says  Mr.  Emmons,  "whether  in  general, 
all  or  even  the  greater  part  of  the  gold  contained  in  placer 


1»> 


gravels  is  derived  from  the  abrasion  of  actual  gold  veins. 
Traces  of  gold  ma}'  be  found  in  a  very  large  proportion  of 
the  massive  rocks  which  form  the  earth's  crust,  ^old  veins 
nre  concentrations  of  this  mineral  in  sufficient  quantity  to 
attract  attention  and  yield  a  profit.  But  doubtless  there 
are  a  vast  amount  of  smaller  concentrations  which  may 
escape  notice.  As  the  rock  disintegrates  and  is  worn  away 
by  atmospheric  agencies,  the  gold  from  these  smaller  de- 
posits as  well  as  from  the  larger  is  set  free  from  its  inclosing 
rock  and  subjected  to  the  concentrating  action  of  mountain 
streams. 

"  Placer  deposits  are  the  results  of  nature's  vast  sluicing 
processes.  To  bring  them  into  the  condition  in  which  they 
may  be  made  available  by  man,  requires  not  only  the  gold- 
bearing  rock,  which  her  agencies  may  grind  u'^  into  sand 
and  gravel,  but  the  sifting  power  of  rapid  streams,  which 
may  carry  down  the  lighter  and  coarser  material,  and  a  suit- 
able channel,  in  which  the  heavier  parti^'les  may  lodge,  as 
in  the  ritHes  of  a  sluice  box.  All  mountain  gravelt^  all  sands 
of  rivers  coming  from  the  mountains,  contain  a  cei'tain 
amount  of  gold,  but  it  is  only  under  peculiarly  favorable 
conditions  that  the  gold  is  so  concentrated  as  to  render  the 
gravel  remunerative. 

"Among  the  most  favorable  of  these  conditions  is  a  com- 
paratively narrow  channel  having  a  hard  and  compact  bed- 
rock, and  ridges  or  bends  in  its  course,  which  by  causing  a 
partial  arrest  in  the  rapidity  of  the  current  shall  allow  the 
heavier  particles  of  gold  to  settle  to  the  bottom,  and  hold 
them  there  when  once  they  have  settled. 

"  From  this  point  of  view  there  is  a  very  evident  reason 
why  California  gulch  should  have  furnisned  rich  placers, 
and  why  the  gold  which  may  exist  in  Iowa  and  Evans 
gulches  should  not  j^et  have  been  extracted  even  though 
the  detrital  material  which  has  been  carried  down  the  gulch 
should  originally  have  been  equally  rich  in  gold. 

"  California  gulch  is  a  valley  of  erosion,  formed  entirel)' 
by  the  action  of  running  water,  and  since  the  glacial  period. 
It  has  therefore  a  bottom  or  bed  of  hard  rock.  Its  trans- 
verse section  is  Y  shaped  and  therefore  favorable  for  the 
concentration  of  heavy  pailicles  at  its  bottom.  When  com- 
paratively full  of  water,  its  numerous  bends  formed  eddies 
in  the  down  flowing  currents,  and  allowed  a  longer  time  at 
these  points  for  the  settling  of  the  surface  p'lrticles,  and  as 
it  cuts  across  many  dififerent  furmations  in  it?:,  course,  its  bed 
must  have  transverse  ridges,  which  have  caught  some  of 


■^  1 

a' 


! 

I 


116 

the  gold  and  prevented  it  from  being  carried  farther  down 
the  stream. 

"  Evans  and  Iowa  gulches  on  the  other  hand  are  glacier- 
carved  valleys.  Their  courses  are  straight,  their  bottoms 
broad  and  comparatively  smooth.  The  glacial  moraine  ma- 
terial with  which  they  are  largely  filled  nas  not  been  sub- 
jected to  the  siftingor  jigging  process  to  which  gravel  is  sub- 
jected in  the  bed  of  a  stream.  The  lower  part  of  their  pres- 
ent beds  is  cut,  not  out  of  rock,  but  out  of  the  loose  gravelly 
formation  of  the  '  Lake  beds.'  This  later  bed,  along  which 
the  material  brought  down  by  post-glacial  erosion  has  been 
carried,  has  not  a  sufficiently  hard  and  permanent  bed-rock 
to  allow  of  Ihe  concentration  of  gold  on  its  surface." 

ALMA   AND    FAIRPLAY    PLACERS,    SOUTH    PARK. 

Along  the  banks  of  the  Platte  river  are  enormous  masses 
of  glacial  morainal  matter  consisting  of  boulders  and  sand 
brought  down  partly  and  principally  from  Mount  Lincoln 
and  receiving  contributions  from  side  glaciers  of  the  Mos- 
quito range.  This  material  forms  undulating  banks  on 
eithei  side  of  the  river.  This  placer  "wash,"  from  50  to 
100  feet  thick,  is  worked  for  gold  principally  at  Alma  and 
Fairpiav. 

At  Alma  the  heavy  bank  of  "wash  "  is  mined  by  the  giant 
nozzle.  The  banks  are  also  cut  back  into  blocks  of  ground, 
by  water  from  a  flume,  which  is  let  out  at  intervals  along 
the  bank  above  ;  at  each  place  it  cuts  a  narrow  ravine  in  the 
loose  debris  and  at  the  same  time  makes  the  banks  easier  to 
be  attacked  by  the  water  of  the  giant  nozzles  which  rapidly 
undermine  them.  The  water  and  sand  from  these  streams 
run  down  into  the  sluices,  whose  bottoms  are  paved  with 
discs  of  wood,  forming  "riffles"  to  catch  the  gold,  whilst 
the  lighter  sand  is  carried  onward  by  the  stream.  In  their 
"clean  up  "  in  the  stream  bed,  they  not  only  wash  down  to 
bed-rock,  but  after  hunting  with  their  knives  in  every  crack 
and  crevice  of  the  latter,  they  dig  it  up  for  a  foot  or  two,  and 
further  examine  't.    The  rock  is  a  jointed  sandstone. 

OuicKsilver  is  thrown  into  the  sluices,  to  collect  the  finer 
gold  which  is  afterwards  retorted.  Whilst  gold  is  found  all 
through  this  bank  of  "wash  "  from  "grass  roots  "  doVv^n  to 
bed-rock,  the  greatest  quantity  of  gold  and  largest  nuggets 
are  found  at  "  bed-rock  "  or  in  its  interstices. 

The  source  of  some  of  this  gold  mav  be  a  series  of  large, 
but  not  very  productive  quartz  veinsjn  granite,  near  Mount 


117 

Lincoln,  whence  the  main  glacier  originated.  It  is  also 
probable  that  a  good  deal  of  the  gold  came,  as  said  before, 
from  the  breaking  up  of  the  various  rocks  in  which  it  was 
disseminated,  more  especialh'  the  porphyries  and  crystalline 
rocks. 

In  the  winter,  owing  to  freezing  of  the  water  supply,  the 
work  has  to  be  discontinued  till  the  following  spring. 


CI      PTER  XJ. 

MINING    REGIONS    SHOWING    EXAMPLES   OF   ORE 

DEPOSITS. 

FISSURE    VEINS   IN    GRANITIC    ROCKS. 

Having  described  in  previous  chapters  the  nature  of  veins, 
ore  deposits,  etc.,  and  how  to  prospect  them,  it  will  be 
of  interest  as  well  as  profit  to  the  prospector,  to  learn 
something  of  the  mines  and  mining  regions  themselves. 
For  this  purpose  we  propose  giving  a  sketch  of  some  of  the 
leading  mining  regions  of  Colorado  and  the  West,  as  in- 
structive illustrations  and  examples  of  what  we  have  writ- 
ten in  previous  chapters.  As  we  said  in  our  advice  as  to  the 
education  of  a  prospector,  the  best  education  for  him  is  to 
go  to,  and  spend  as  much  time  as  he  can  in,  the  mines  and 
mining  regions  themselves. 

We  will  take  first  the  regions  characterized  by  fissure 
veins.  These  veins  are  in  the  granitic  and  igneous  districts 
of  Colorado.  In  the  granitic  ranges,  the  mining  districts  of 
Boulder  county,  Gilpin  and  Clear  Creek,  are  the  most  noted, 
the  principal  mining  towns  being  Boulder,  J  imtown,  George- 
town, Central  and  Idaho  Springs. 


HOULDER   MINES. 

The  geological  features  of  Boulder  consist  in  a  series  of 
ridges  or  hogbacks  rising  up  from  the  prairie  and  flanking 
the  granite  mountains.  These  represent  Mesozoic  strata 
consisting  of  sandstones,  limestones  and  shales,  containing 
beds  of  coal  and  other  economic  products,  but  no  precious 
metal.     Volcanic  action   has   occurred  in   their  vicinity  as 


ii8 

shown  b}-^  a  large  dyke  of  basalt  at  Valmont.  These  hog- 
backs, so  universally  present,  flanking  the  granite  mountains, 
are,  in  Colorado,  destitute  of  precious  ores.  Inside  of  and 
west  of  these  is  the  Archa3an  granitic  front  range,  C(jnsisting 
of  heavil}^  bedded  granite-gneiss,  profusely  traversed  by 
veins  of  "  pegmatite  "  or  very  coarse  sparry  granite,  consist- 
ing of  white  feldspar  and  quartz,  with  very  little  mica,  and 
from  a  few  inches  to  40  or  50  feet  in  width  ;  with  these  also 
occur  some  dykes  of  eruptive  rock,  some  of  it  a  dark  black 
rock  like  basalt,  called  "diabase";  others  are  lighter  col- 
ored quartz  porphj-ries  and  diorites.  In  the  telluride  belt, 
whilst  pegmatite  veins  are  abundant,  eruptive  rocks  are 
scarce,  but  west  of  the  telluride  belt,  which  is  more  or  less 
confined  to  a  special  area  underlying  the  Magnolia,  Sugar 
Loaf,  Gold  Hill  and  Central  districts,  enormous  masses  of 
eruptive  rock  are  found,  but  no  tellurides.  In  the  non-tellu- 
ride  districts,  such  as  Caribou,  Ward  and  Jimtown,  rich  silver 
ores  are  found  associated  with  galena,  gray  copper,  etc., 
and  gold  ores  associated  with  copper  and  iron  pyrites. 
Thus  there  are  two  or  three  distinct  belts  in  the  region, 
a  telluride  gold  belt,  and  a  silver  belt,  and  a  gold  pyrites 
belt.  It  is  noticed  that  the  entire  region  has  been  locally 
disturbed  b)^  volcanic  forces,  and  volcanic  rocks  abound  ; 
outside  of  this  disturbed  region  there  are  no  mines  for  a 
lonfT  distance. 

ihe  Boulder  mines  are  celebrated  for  the  occurrence  of 
telluride  minerals,  some  of  the  richest  and  rarest  ores  oc- 
curring in  npture.  These  ores  are  confined  to  a  belt  occupy- 
ing the  eascern  part  of  the  district,  and  nearer  to  the  hog- 
back region  of  the  plains  than  any  other  important  ore 
deposits  in  Colorado. 

West  of  this  belt  in  the  Caribou  district  the  ores  are 
argentiferous  galena,  with  brittle  silver.  In  the  Ward  dis- 
tiict  pyrites  ;il^ound,  and  where  it  is  decomposed  the  gold  is 
free.  The  pyrites  though  gold-bearing  are  difiicult  of  re- 
duction. 

The  pegmatite  veins  containing  the  ore  stand  at  a  high 
angle  and  are  often  very  wide,  but  the  rich  ores,  especially  the 
tellurides,  arc  concentrated  in  thin  streaks  and  not  very  con- 
tinuous bodies.  The  gangue  or  vein  material  is  simply  an 
alteration  of  the  adjacent  granite,  or  gneissic  country  rock, 
into  a  more  sparry,  larger  crystalline  form,  consisting  of 
quartz,  feldspar,  and  %ome  mica.  This  is  impregnated  with 
rich  mineral,  whose  source  is  probably  not  far  to  find,  the 
metal  elements  being  microscopically  or  chemically  diffused 


119 


throuf^h  the  mineral  elements  composinji^  the  adjacent 
countn'  rock,  which  is  sometimes  porphyry,  and  at  others 
gneiss.  This  impregnation  has  taken  place  either  along  the 
contact  of  an  eruptiv^e  rock  with  the  country  rock  granite, 
or  else  in  a  pre-existing  vein  of  pegmatite,  or  along  some 
fault  or  jointing  plane  in  the  country  rock  itself  which  has 
been  favorable  to  the  concentration  and  precipitation  of 
metallic  minerals  from  their  solutions.  The  direction  of  the 
vems  is  generally  between  Northeast  and  Northwest,  or 
East  and  West ;  their  dips  are  steep  or  vertical. 

The  quartz  of  the  pegmatite  gangue,  when  impregnated 
with  telluride  ore,  '.  s  a  pale,  bluish-gray  and  rather  greasy 
appearance,  streaked  here  and  there  with  a  dull,  blackish, 
greasy  stain,  upon  which  sometimes  the  true  telluride  min- 
erals such  as  sylvanite,  can  be  seen,  generally  in  long  thin 
crystals  of  a  bright  tin-like  appearance.  It  is  sometimes 
called  graphic  tellurium,  because  the  crystals  crossing  one 
another  assume  'uhe  form  of  Hebrew  characters,  Syh^anite 
is  a  telluride  of  sliver  and  gold.  There  are  many  varieties 
of  telluride,  some  rich  in  silver  and  others  in  gold,  and  some 
with  both  combined.  When  a  piece  of  gangue  containing 
tellurium  is  roasted,  the  gold  comes  out  in  good  sized 
globules  on  the  surface. 

Two  great  mother-veins,  called  the  Maxwell  and  Hoosier 
veins,  traverse  the  telluride  district  for  sev^eral  miles,  easily 
traceable  by  their  rusty  color.  One  carries  pyrites  and  tellur- 
ides,  the  other  silver  ore  and  gray  copper.  Gold  Hill  dis- 
trict, in  the  telluride  belt,  is  traversed  by  the  Hoosier  gangue. 
Several  veins  cross  the  Hoosier  gangue  and  are  richer  in  its 
vicinity  ;  in  some,  the  ore  is  a  telluride  at  the  surface,  but 
with  depth  passes  down  into  gold-bearing  pyrites. 

The  Ward  district  outside  the  telluride  belt  carries  copper 
and  iron  pyrites  bearing  gold.  Caribou  is  silver-bearing,  its 
ores  are  galena,  copper  pyrites  and  zinc-blende  occurring  in 
gneiss  near  a  dyke  of  eruptive  diabase.  The  No-Name  vein 
crosses  and  faults  the  Caribou  vein.  Its  ores  carry  both 
silver  and  gold ;  the  ores  are  silver  glance,  brittle  silver, 
gray  copper,  galena,  copper  pyrites,  with  native  and  ruby 
silver.     The  copper  pyrites  carries  more  gold  than  silver. 

The  granitic  rocks  near  Boulder  are  thrown  into  a  series 
of  parallel  folds,  one  series  cut  diagonally  by  another.  The 
telluride  veins  run  along  the  slopes  of  these  folds.  The 
veins  are  in  cracks  and  fissures  coinciding  with  this  folding, 
some  of  the  main  fissures  being  filled  at  once  by  porphyry 
dykes,  the  others  more  gradually  by  vein  material.    The 


ISO 


veins  occur  along',  on,  and  near  these  dykes,  al(jng-  lines  at 
the  junction  of  the  more  massive  g^rani'te  with  the  bedded 
gneiss,  along  and  between  stratification  planes  of  schist, 
and  along  the  joint  planes  of  granite.  The  veins  are  due  to 
percolating  alkaline  waters  dissolving  metalliferous  material 
and  veinstone  from  the  surrounding  rocks.  It  is  nijteworthy 
that  alkaline  springs  still  exist  in  the  neighborhocjd,  as  they 
do  also  at  the  mining  district  of  Idaho  Springs.  The  veins 
occur  where  the  foldings  are  abrupt,  and  the  direction  of  the 
veins  is  parallel  to  the  strike  of  the  stratification.  As  a  rule 
the  veins  are  not  of  great  extent.  A  single  vein  can  rarely 
be  traced  on  the  surface  or  beneath  it  for  more  th;  n  600 
feet.  Before  that  distance  is  reached,  the  vein  spi  j  oft 
again  into  another. 

Where  veins  cross  at  a  small  angle  or  where  a  spur 
branches  off  from  the  main  vein,  accumulation  and  enrich- 
ment of  ore  takes  place.  There  are  two  courses  of  \-eins, 
one  East  and  West,  the  other  Northeast  by  Southwest ; 
the  former  S3'stem  appears  to  be  the  older  as  the  latter 
faults  it. 

The  ore  occurs  in  chimneys  or  pockets,  with  a  good  deal 
of  barren  ground  between. 

Small  veins  run  parallel  with  each  other  for  some  dis- 
tance, the  interval  filled  with  granite  or  pegmatite.  Some- 
times a  vein  pinches  out  entirr^ly  (contrarj'  to  the  general 
habit  of  true  large  fissure  veins  occupying  great  fault 
fissures).  The  ore  streak  is  from  i  to  20  inches  wide  con- 
taining more  of  this  blue,  greasy,  fine  grained  "horn  quartz" 
than  the  country  rock.  Some  of  the  veins  interlace  iike 
arteries  in  a  human  body.  Minui^  particles  of  pyrites 
(marcasite)  often  produce  the  dark  stains  we  have  noted  on 
the  telluride  quartz.  By  moistening  the  stone,  the  telluride 
minerals  and  pyrite  appear  distinctly. 

A   TYPICAL  BOULDER  COUNTY   MINE. 

A  good  typical  and  very  instructive  example  of  a  contact 
fissure,  gold-bearing  vein  is  that  of  the  Golden  Age  at  Jim- 
town,  north  of  Boulder. 

"At  Jimtown  a  quartz-diorite  dyke  occurs,  of  light  color 
containing  much  hornblende  and  titanic  iron,  running  nearly 
through  the  street  of  the  village.  The  cliffs  at  Jimtown, 
over  500  feet  high,  are  of  quartz  porphyry,  of  white  color, 
consisting  mainly  of  large  crystals  of  quartz  and  feldspar, 
set  in  a  fine  grained  crystalline  ground  mass  or  paste. 


121 


I 


(;()1.I)EN    AOK,   AND   SKNTIXEL   VEINS. 

From  the  town,  the  road  winds  up  a  steep  mountain  com- 
pcsed  of  coarse  gray  granite,  with  occasional  belts  (jf  gneiss. 
Here  are  located  the  Golden  Age  and  Sentinel  mines. 

The  Golden  Age  covers  the  outcrop  of  a  (juartz-porphyry 
dyke  cutting  through  the  granite.  This  dyke  vanes  in 
width,  from  a  few  Teet  to  about  fifty.  The  outcrop  of  the 
main  ore  chute  of  the  Golden  Age  extends  along  the  "con- 
tact "  on  the  lower  side  of  the  porphyrv  dyke.  At  a  depth 
of  IOC  feet  the  main  shaft  discloses  a  split  in  the  vein.  The 
hanging  wall  of  the  ^'ein  continues  into  the  dyke,  but  with 
jiorphyrj'  hanging  and  footwalls,  until  a  depth  of  330  feet, 
where  it  enters  the  upper  contact  between  the  porphyry 
and  granite.  The  dyke  has  been  much  acted  upon  and 
decomposed  by  vein  forming  agencies  in  the  upper  work- 
ings, but  in  the  lower  it  is  less  decomposed  and  shows  con- 
siderable pyrites.  The  Golden  Age  veins  are  well  defined, 
presenting  a  banded  or  ribbon  structure.  They  are  inclosed 
in  distinct  walls  with  gouge  or  selvages,  which  at  times 
show  slickensides.  The  seams  and  feeders  that  have' 
enriched  both  veins  come  in  from  the  porphyry  dyke. 

The  ore  from  the  Golden  Age  contains  rich  and  magnifi- 
cent specimens  of  free  gold  It  is  a  free  milling  ore.  When 
rich,  the  gangue  is  a  hard,  flinty,  vitreous  white  quartz. 
The  gold  is  seldom  accompanied  by  pyrites.  It  is  generally 
imbedded  in  the  white  quartz  as  bright  yellow  gold,  in  size, 
from  coarse  grains  to  nuggets  several  ounces  in  weight; 
after  it  reaches  the  lower  contact  between  the  porphyry 
and  granite  and  enters  the  granite,  there  is  an  increase  in 
the  baser  metals,  such  as  zinc-blende,  galena  and  pyrites, 
but  the  ore  still  retains  its  value  in  free  gold. 

Returning  to  the  surface,  ■'he  Sentinel  location  covers 
the  apex  of  a  vein,  which  there  appears  enclosed  in  a  belt 
of  schistose  or  gneissic  rock. 

This  vein  dips  South  at  an  angle  of  70°  and  passes  through 
the  Golden  Age  vein  on  its  course. 

The  Sentinel  vein  ore  is  entirely  distinct  from  that  of  the 
Golden  Age.  It  is  the  characteristic  bluish  horn  quartz  of 
the  tellurium  veins  of  Boulder  County,  with  characteristic 
chalcedony  quartz  crystals  and  finely  disseminated  pyrites. 
The  value  is  in  metallic  gold  and  such  tellurium  ores  as 
petzite  and  sylvanite.  Whilst  most  of  the  gold  was  deposited 
as  native  gold,  a  portion  has  evidently  been  rendered  free 
by  partial  decomposition  of  the  tellurides.    This  ore  is  very 


122 

rich.  The  richest  ore  usually  occurs  in  two  narrcnv  seams 
or  streaks  from  a  foot  to  ten  feet  apart,  the  intervening- 
space  being  more  or  less  mineralized  country  rock.  It  is 
richest  when  in  the  schistose  rock,  and  poorest  when  it 
passes  through  the  porphyry  dyke.  The  crossing  of  the 
Sentinel  vein  through  that  of  the  Golden  Age  is  very  clearly 
marked ;   it  very  slightly  faults  the  Golden  Age  vein. 

The  gold  mines  of  Boulder  County  belong  to  two  distinct 
periods  of  vein  formation  ;  to  one  beh^ng  the  non-telluride 
ores,  and  to  the  other  those  producing  tellurium.  The 
tellurium  veins  appear  to  be  the  later  of  the  two. 

The  ores  of  the  Sentinel  tellurium  vein  are  lower  grade 
where  the  vein  passes  through  the  porphyry  dyke.  This  is 
due  to  the  Golden  Age  vein  being  formed  first,  and  drain- 
ing the  dyke  of  its  disseminated  mineral  values.  The 
Sentinel  received  its  mineral  from  the  schistose  or  gneissic 
rocks,  and  is  consequently  richer  where  enclosed  in  those 
rocks  than  when  in  the  dvke. 


Vein 


Plate  LXIX. 

Section  of  Golden  Age  Vein,  Jimtown,  Boulder  Co.,  Colo. 

Prospectors  look  for  richer  or  larger  bodies  of  ore  when 
veins  unite  or  cross  each  other.  In  the  Golden  Age  the 
two  veins  unite  about  loo  feet  below  the  surface.  There 
are  similar  veins  of  the  same  age,  and  large  and  rich  ore 
bodies  are  found  at  their  junction.  On  the  other  hand,  the 
Sentinel  vein  of  later  age,  passing  through  the  earlier 
Golden  Age  vein,  produced  no  enrichment  of  the  ore  bodies. 


1^3 

To  form  such  ore  bodies,  the  veins  should  be  of  contempo- 
raneous origin." 

The  ore  deposits  of  (Jilnin  and  Clear  Creek  Counties  are 
\'ery  similar  to  those  of  IJoulder,  only  they  do  not  produce 
tellurium  ores.  The  country  rock  is  the  same  granite-gneiss, 
penetrated  here  and  there  by  porphyry  dykes.  The  peg- 
matitic  veins  are  either  in  the  gnefss  or  between  the 
dykes  and  the  granite.  In  some  cases  the  porphyry  dyke 
Cfjnstitutes  a  vein  in  itself,  such  as  the  Minnie,  which 
is  a  felsite  porphyry,  and  the  Cyclops,  a  quartz  porphyry, 
In  (iilpin  county,  around  Central  City,  the  ores  are  a  mixture 
of  copper  nyrite  and  iron  pyrite  with  a  very  little  galena 
and  zinc-blende.    All  are  gold-bearing. 

The  richer  ore  occurs  in  streaks  not  over  a  foot  wide,  in  a 
compact,  fine  grained  mass  of  pyrite.  Copper  pyrite  is 
richer  than  iron  pyrite.  The  rest  of  the  vein,  often  manv 
feet  wide,  carries  pyrite  irregularly  disseminated  through 
decomposed  country  rock.  The  bulk  of  these  ores  are 
difficult  to  treat,  and  are  milled,  the  loss  being  40  per  cent, 
higher  in  the  unoxidized  ores  than  in  the  oxidized.  The 
veins  follow  the  cleavage  planes  of  the  gneiss,  cutting  the 
stratification  planes  at  right  angles  with  a  vertical  din.  The 
porphyry  dykes  are  older  than  the  veins,  as  the  cleavage 
planes  intersect  both  the  porphyry  and  gneiss  alike.  For  an 
interval  of  20  miles  between  these  mining  districts  and  the 
plains,  there  are  no  ore  deposits  of  any  importance  known. 

In  Clear  Treek  County  the  ores  are  mainly  silver-bearing  ; 
the  silver  is  derived  mainly  from  galena  and  gray  copper. 
Dykes  of  obsidian  occur  in  one  of  the  mines  parallel  with 
the  vein,  which  is  itself  a  porphyry  dyke.  The  richest  min- 
eral is  close  to  the  obsidian  dyke. 


FISSURE   VEIN.S   IN   TRUE   IGNEOUS   ROCKS. 

Whilst  most  of  our  fis?:ure  veins  and  ore  deposits  gener- 
ally are  more  or  less  associated  with  the  presence  of  igneous 
rocks,  there  are  some  which  are  essentially  in  igneous 
eruptive  rocks  alone. 

The  most  remarkable  of  these  are  the  fissure  veins  of  the 
San  Juan  region  in  southwestern  Colorado. 

This  region  consists  of  an  enormous  plateau  of  lavas  of 
great  thickness  resting  upon  and  originally  overflowing  a 
a  low  mountain  range  or  plateau  of  granitic  and  upturned 
sedimentary  rocks,  the  latter  representing  most  of  the 
geologic  periods  from  Cambrian  to  Tertiary.    The   hickness 


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124 

of  these  j^reat  lava  flows,  wliich 
were  erupted  at)(nit  the  Eocene 
period  of  the  Tertiary,  is  upwards 
of  1.500  feet;  tiiis  lava  mass  has 
been  cut  up  by  glacial  and  river 
action  by  profound  canyons,  into 
a  rups'ed  mountain  ran«i;^e.  the 
summits  of  some  of  the  castel- 
lated mountains  reaching  a  heij>fht 
of  14.000  feet  above  tiie  sea.  The 
lava  sheets  are  also  tra\'ersed  to  a 
depth  of  1,500  feet  more  or  less, 
by  an  extraordinary  number  of 
f^^reat  quartz-fissure  veins.  These 
veins  appear  to  till  shrinkaf>^e 
cracks  resulting  from  the  con- 
traction on  co(jling  of  the  lava 
sheets,  strictly  speaking  they  are 
rather  "gash  \'eins"  on  a  larger 
scale  than  "  true  fissure  \'eins." 
fc^r  they  are  mostly  Itmtted  to  the 
thickness  of  the  laTa  o^rrjliru's  and 
cease  when  they  reach  the  under- 
1\  ing  granite. 

There  appear  to  have  been  two 
principal  eruptions;  the  first,  dur- 
ing the  early  part  of  the  Tertiary, 
covered  the  higher  region  of  the 
San  Juan  mountains  to  a  depth 
of  1,500  feet  with  an  overflow  of 
brecciated  andesitic  lava,  which 
on  cooling  developed  fissures  of 
contraction  traversing  the  lava 
mass  in  all  directions;  these  were 
subsequently  and  slowly  filled 
with  a  hard  bluish  quartz  contain- 
ing more  or  less  ore. 

Following  the  first  grand  over- 
flow were  others  of  less  magni- 
tude, consisting  of  non-brecciated 
andesites  and  rhyolites.  This  sec- 
ond dynamic  movement  produced 
locally,  fissures  extending  below 
the  horizon  of  breccia  into  the 
stratified  rr,cks,    These,  however, 


12 


5 


are  selfloiii  productive  below  the  eruptive  zone.  There  are 
also  metal  deposits  in  connection  with  still  older  eru|)tions 
ot  andesite  and  diorite.  such  as  Mineral  Kariu.  Calliope,  etc. 


RED    MOUNTAIN. 

In  the    Red   Mountain   district   the   ore  deposits  form  a 
])eculiar  group.     They   occupy   a   series   of    more    or  less 


126 

C()n?iocted  inojijular  chambfrs,  trciulin^flowiiwaifl,  pmhahly 
channels  of  ancient  hoi  mineral  spring's,  'I'lie  niinerah/inif 
water  completely  silicilied  the  surrounding^  erupti\e  rocK 
for  some  (hstance  away  from  tlu'  ore  chambers.  So  the  ore 
bodies  are  distributed  throuj,'ii  a  hu^rf  jiivjrular  column  of 
quartz  extondinjj^  to  an  undetermined  depth. 

Larja^e  masses  of  brilliantly  colored  ..laterial  are  conspicu- 
ous in  this  region.  'I'hey  have  been  acted  upon  by  mineral 
waters  circuhitiiifj^  throujj^h  their  crannies  and  lissures,  Ore 
bodies  are  occasionally  found  in  these  and  such  mini's  are 
locally  known  as  cave  mines. 

The  ores  of  the  San  juan  are  mostly  arj^entiferous  f^ray 
copper,  copper  pyrites  and  jj^alena  associated  with  zinc- 
blende  and  iron  jtyrites  in  usuallya  hard  horn-(piartz  matrix. 
Some  of  the  ore  locally  contains  a  hif>^h  per  centaj^e  of  bis- 
muth; others  produce  pyrar^yrite  ann  polybasite,  rich 
silver  minerals;  others  carrv  considerable  ^o\(\,  such  as  the 
recently  discovered  gold  belt  at  Ouray.  This  belt  occurs  in 
Dakotah  Cretaceous  sandstone,  which  has  been  altered  into 
a  quartzite  by  the  intrusion  of  dykes  and  sheets  of  erujitixe 
diorite.  One  of  these  sheets  spreads  out  in  the  (piartzite. 
The  ore  occurs  at  the  top  of  the  quartzite,  at  its  junction 
with  a  bed  of  shale.  The  fj^old,  which  is  free  and  enclosed 
in  brown  oxide  of  iron,  doubtless  orig-inated  from  the  |ior- 
phyry,  and  entered  the  joints  and  beddinj^  planes  of  the 
quartzite,  where  they  were  opened  by  faulting.  Aboxe  the 
shale  the  ore  does  not  penetrate,  the  shale  acting  as  an 
impervious  resistance  to  uprising  solutions.  Ore  bodies 
also  occur  in  the  Jurassic  limestones  below  the  ([uartzite, 
especially  where  they  are  penetrated  by  eruptive  rocks. 

In  the  eastern  portion  of  the  San  Juan  region  some 
important  gold  deposits  occur  near  Del  Norte  in  the  Little 
Annie  or  Bovv'en  Mine,  which  appear  to  be  a  decomposed 
dyke  of  eruptive  rock,  containing  free  gold  in  brown  iron, 
in  the  upper  portion,, and  with  depth  iron  pyrites  also  gold- 
bearing. 

CREKDE. 

At  the  newly  discovered  camp  of  Creede,  not  very  far 
from  Del  N(jrte,  the  fissure  veins  are  very  similar  in  char- 
acter to  those  elsewhere  in  San  Juan;  they  are  quartz 
fissure  veins  traversing  andesitic  breccia  and  other  volcanic 
rocks.  The  gangue  matter  in  the?"  veins  is  exceedingly 
rich  in  silver-bearing  ore,  so  much  so  that  the  amethystine 
quartz   composing   the   gangue   or  veinstone  is  quite  in  a 


■■■t 

1: 


127 

minority  to  the  ore,  and  the  vein  may  be  said  to  be  nearly  a 
mass  ot  ore  from  wall  to  wall.  The  thick  lavas  of  Crced*^ 
rest  donbtless  with  deptli  npon  ("arhoMiterous  limestone  ot 
else  on  bare  granite  ;  the  fornu-r  is  found  outcroppinj^  at 
some  distance  from  Creede,  from  beneath  the  lava  overtlow, 
and  bi'in^  penetratinl  by  intrusive  rruptive  rocks  shows 
sijj^ns  here  and  there  of  prorhictive  ore  deposits  similar  prob- 
ably to  those  at  Leadville.  Creede  is  an  encoura^inj^ 
example  to  a  prospector,  that  all  productive  veins  in  Colo- 
rado lia\'e  not  been  discovered  yet.  e\'en  in  districts  that 
ha\e  been  pretty  well  tramped  o\'er.  Creede  had  doubtless 
')ften  been  more  or  less  walked  over  bv  prospectors  for 
vcars  before  the  jj^reat  discovery  was  made,  and  in  a  ye'ar's 
time  we  may  hear  of  several  more  similar  discoveries  in  the 
jj^reat  San  Juan. 

ROSITA    AND    SILVKR    CI.II  F. 

The  next  important  and  peculiar  ijj^neous  district  carryinjj^ 
lissure  \'eins  is  that  of  Rosita  and  Silver  ClitT  in  the  Wet 
Moup.tain  Valley  near  the  edge  of  the  prairie  country  in 
southeastern  Colorado.  Here  a  local  eruption  of  consider- 
able power  and  magnitude  and  of  comparatively  recent  date 
has  occurred.  These  eruptions,  consisting  of  andesitic, 
rhvolitic  and  trachytic  material  have  built  up  cones  and 
rounded  b.ills  largely  of  fragmental  material  such  as  consoli- 
dated tuffs.  ashe«,  and  breccia,  all  of  which,  as  at  Cripple 
Creek,  rest  on  granitic  basement  rock.  From  the  fragmen- 
tary character  of  th(i  rocks  it  is  evident  that  most  of  the 
t^ruptions  were  explosive,  alternating,  however,  with  quieter 
flows;  in  some  cases  the  dykes  can  be  seen,  where  some  of 
the  lava  came,  at  others  the  "necks"  or  throats  of  the 
volcanoes  themselves  filled  up  with  volcanic  boulders;  of 
such  is  the  celebrated  Bassick  Mine.  The  mine  is  in  the 
throat  of  ai^  old  crater  of  andesite,  tilled  with  boulders  of 
granite  and  andesite  bedded  in  gravel  and  sand.  The  ore  of 
the  Bassick  appears  as  concentric  /ones  or  shells  around 
these  boulders,  as  a  replacement  of  the  gravelly  matrix. 
The  entire  mass  has  been  permeated  by  heated  waters  which 
have  decomposed  the  rocky  fragments,  depositing  opaline 
quartz  and  kaolin  in  abundance. 

The  concentric  shells  around  the  boulders  carry  alter- 
nately several  minerals, such  as  galena, antimony,  zinc-blende, 
copper  and  iron  pyrites,  all  more  or  less  gold-bearing.  The 
ore  deposition  in  this  region  seems  to  have  taken  place  at 
the  close  of  the  eruptive  period,  when  tfic  eruptions  were 


It 


128 


dying-  out  into  hot  sprinj^s,  fumaroles,  etc.,  and  producing^ 
great  decomposition  ot  the  lava  rocks.  The  district  was 
not  thought  much  of,  until  Mr.  Bassick  made  his  discovery 
in  the  unpromising  looking  throat  of  the  old  volcano,  con- 
taining a  formation  quite  anomalous,  and  which  the  regular 
prospector,  "ccustomed  to  true,  orthodox  fissure  veins, 
would  have  passed  by  as  very  unlikely.  So  it  may  happen 
to  future  prospectors,  that  some  very  unlikely  formations 
may  turn  out  great  riches ;  hence  it  is  well  to  keep  a  sharp 
lookout  for  everything  examinable. 

A   STUDY  OF   MODERN    LIVING    VOLCANOES   TO    UNDERSTAND 
THE   CRIPPLE   CREEK    VOLCANO. 

Bv  far  the  most  tvpical,  instructive  and  important  gold 
camp  in  Colorado  and  the  West  is  that  of  Cripple  Creek.  To 


'S^.'^iiiMM'' 


Plate  LXXII. 

Stromboli  Volcano. 

understand  the  geology  of  the  Cripple  Creek  region  and 
gold-bearing  volcanic  regions  and  rocks  and  their  relations 
to  the  ore-deposits,  a  knowledge  of  the  phenomena  attending 
modern  volcanic  eruptions  is  necessary.  Let  us  take  that  of 
the  living  volcano  of  Stromboli,  described  by  Professor  J  udd, 
as  throwing  some  light  on  the  phenomena  that  may  have 
occurred  many  thousands  of  years  ago  in  the  now  extinct 
volcano  of  the  Cripple  Creek  district. 

From  a  point  on  the  sides  of  the  mountain  of  Stromboli, 
masses  of  vapor  issue  and  unite  to  form  a  cloud  over  the 
mountain.  This  cloud  is  made  up  of  globular  masses,  each 
of  which  is  the  product  of  a  distinct  outburst  of  the  volcanic 
forces.  At  night  a  glow  of  red  light  appears  on  the  cloud, 
increasing  gradually  in  intensity,  and  as  gradually  fading 
away. 


129 


After  an  interval  this  is  repeated  and  continues  till  the- 
light  of  dawn  causes  it  to  be  no  longer  visible.  When  we 
land  on  the  island  we  find  it  built  up  of  the  "ejecta"  from 
the  volcano  like  a  gigantic  iron  furnace  with  its  heaps  of 
cinders  and  masses  of  slag.  The  irregular  shape  and  surface 
of  the  island  is  due  to  erosion  removing  the  loose  materials 
at  some  points,  and  leaving  the  hard  slaggy  masses  standing 
up  prominently  as  dykes  and  hard  portions  of  lava  flows,  as. 
Pisgah,  Rhyolite  Mt.  and  others  at  Cripple  Creek  do,  above 
the  eroded  and  more  fragmentary  tuffs  and  breccias.  This 
great  heap  of  cinders  and  slags  rises  6,000  feet  above  the  sea 
bottom  with  a  base  four  miles  in  diameter;  2,000  feet  above 
sea  level  is  a  circular  depression,  the  crater  of  the  active 
volcano. 

Looking  down  into  the  crater,  an  outburst  takes  place. 
Before  the  outburst,   many  light  curling  wreaths  of  vapor 
ascend  from  fissures  on  the  sides  and  bottom  of  the  crater. . 
Possibly  this  is  the  origin  of  some  of  the  dyke-filled  fissures- 
of    Cripple    Creek. 
Suddenly  a   sound  is 
heard  like  a  locomo- 
tive  blowing    off    its 
steam.      A    great 
volume   of    watery 
vapor   is    thrown   up 
into  the  atmosphere, 
and  with  it  a  number 
of  dark  fragments  are 
hurled  500  feet  above 
the  crater,  some  fall- 
ing on  the  mountain, 
others  back   into  the 
crater    with     a    loud 
rattling  noise.    Those 
rolling    down    the 
mountain  are  still  hot 
and      s  em  i-molten. 
This  is  a  clue  to  the 
origin  of  the  fragmentary  materials  composing  the  tuffs  andl 
breccias  at  Cripple  Creek.    The  black  slaggy  bottom  of  the 
crater  is,  as  we  nave  said,  traversed  by  many  fissures  emit- 
ting jets  of  vapor.     Some  of  these  are  quite  large  and  vary  in 
size  and  number  and  position  at  different  periods.     From 
some,   only  steam    is   emitted   in    loud   snorting  puffs.     In 
others  molten  material  is  seen  welling  up  and  flowing  out— 


Plate    LXXIII. 

Map  of  Island  of  Stromboli. 


I30 


side  the  crater.     Such  fissures  when  all  eruption  has  ceased 
would  be  found,  as  at  Cripple  Creek,  sealed  up  with  solid 


Plate  LXXIV. 

Stromboli  Crater. 

lava  with  a  lava  flow  on  their  tops.  From  this  liquid  mass, 
steam  escapes  in  considerable  quantities.  Within  the  walls 
of  the  fissures,  a  viscid  semi-liquid  'av?  heaves  up  and  down 
and  churns  around  till  at  last  a  gig.  itic  bubble  or  blister  is 
formed  which  bursts  violently  and  a  great  rush  of  steam 
takes  place  carrying  fragments  of  the  scum-like  surface  Ol 
the  liquid  high  into  the  air.  At  night  the  fissures  glow  with 
ruddy  light.  The  liquid  matter  is  white  hot  and  the  scum  on 
it  a  dull  red.     Every  time  a  bubble  bursts  a  fresh  glowing 

is  the  ver.ection  of  this   upon  the 
clouds     of     steam 


surface  is  exposed.     It 


above  the  mountain 
that  causes  the  fitful 
glows  of  light  we 
mentioned. 

The  phenomena 
show  there  are 
cracks  communicat- 
ing with  the  earth's 
interior  highly 
heated  matter  be- 
neath the  surface, 
together  with  great 
quantities  of  impris- 
oned water,  wliich 
escaping  as  steam  give    rise  to  all  the  active  phenomena. 


Pl.ATK  LXXV. 

Dykes  Cutting  Beds  of  Scoria  and  Tuff  in  the 
Wall  of  a  Crater. 


131 

What  is  pv)pularly  supposed  to  be  flame  in  an  eruption  is 
the  reflection  on  the  cloud  of  steam  and  dust,  from  g^lowing- 
masses  in  the  mouth  of  the  crater.  Sulphur  is  not,  as 
commonly  supposed,  erupted  from  a  volcano,  but  is  formed 
by  the  union  of  sulphurous  acid  and  sulphureted  hj'drogen 
issuing  from  vulcanic  vents. 

A  volcano  is  a  steam  vent,  like  a  geyser,  which  may  be 
called  a  water  volcano. 


■     ORIGIN   OF   FISSURES. 

Some  light  is  thrown  on  the  possible  origin  of  som-e  of 
the  Cripple  Creek  dykes  and  fissures  by  the  eruption  of 
Vesuvius  in  1872.  The  bottom  of  the  crater  was  entirely 
broken  up  and  the  sides  of  the  mountain  rent  by  fissures  in 
all  directions.  So  numerous  were  these  fissures  that  liquid 
matter  appeared  to  be  oozing  from  every  part  of  its  surface 
and  the  mountain  to  be  "sweating  lire."  One  fissure  was 
enormous,  extending  from  the  summit  to  far  beyond  the  base 
of  the  cone.  This,  filled  with  a  dyke  of  hn  a,  is  visible  to-day. 
From  both  crater  and  fissures  enormous  volumes  of  steam 
rushed  out  with  a  prodigious  roar.  This  roaring  was  from 
explosion  of  bubbles  one  after  another,  and  the  vapor  cloud 
above  Vesuvius,  as  at  Stromboli,  was  made  up  of  globular 
masses  of  steam  ejected  at  successive  explosions.  Each 
explosion  carried  upward  quantities  of  fragments  which  fell 
back  on  the  mountain.  All  along  the  course  of  the  stream 
of  lava,  volumes  of  steam  were  thrown  off. 


ORIGIN    OF    TUFFS. 

The  discharge  of  such  large  quantities  of  steam  causes 
the  atmosphere  to  be  saturated  with  watery  vapor,  which, 
condensing,  falls  in  excessive  rain  storms,  producing  mud 
streams  formed  by  rain  water  sweeping  along  the  loose  vol- 
canic dust  and  debris.  In  some  such  way,  doubtless,  the 
Cripple  Creek  tuflfs  and  breccias  were  formed. 

GASES   AND   MATERIALS    EJECTED    FROM    VOLCANOES, 

The  most  abundant  of  the  substances  ejected  from  vol- 
canoes is  steam,  and  wiih  it  many  volatile  materials,  such  as 
hydrochloric  acid  and  carbonic  acid,  also  hydrogen,  nitro- 
gen and  ammonia,  and  at  Cripple  Creek  fluorine  gas. 

These  different  gases  at  Cripple  Creek  had  much  to  do 
with  the  formation  of  ore  deposits.    Volatile  metals,  such  as 


132 


II 


•arsenic,  antimoii)'  and  cinnabar  are  erupted ;  these  sub- 
stances, issuing  from  volcanic  vents  at  high  temperature, 
react  upon  one  another  forming  new  compounds,  such  as 

•sulphur.  Hydrochloric  acid  unites  with  the  iron  iri  the 
rocks  to  form   yellow  ferric  chloride,  common  at  Cripple 

<Creek'.  and  looking  like  a  greenish  yellow  sulphui      Acid 


Plate  LXXVI. 

Plan  and  Cross-Section  of  the  ''^""ts  of  a  Crater.    Blacks  Dykes  Filling  Fissures. 

•gases  change  lime,  alkaline  and  iron  elements  into  sulphates, 
•chlorides,  carbonates  and  borates,  which,  when  removed  by 
rain,  leave  a  white  substance  like  chalk,  composed  of  pure 
•silica.  Beds  of  such  material  occur  not  far  from  Cripple 
«Creek  and  powdered  silica  in  some  of  the  mines. 

The  lips  of  fissures  from  which  steam  and  gases  issue  are 
•  coated  with  yellow  and  red  incrustations  of  sulphide  and 
oxide  of  iron,  such  as  are  common  in  many  prospect  holes 
sit  Cripple  Creek. 


■8WW- 


133 


Solid  materials  are  ejected  in  vast  quantities  ;  fragments 
of  the  rock  masses  through  which  the  fissure  is  rent  are 


Microscopic  Structure  of  Glassy  Lava  Showing  Microlites  and  Crystallites. 


Microscopic  Structure  of  Some  Crystals  Showing  Microlites  and  Crystallites. 

Plate  LXXVII. 

carried  upwards  by  the  steam  blasi,  together  with  other 
matters  far  beneath  the  surface  in  a  semi-fluid  condition. 
Hence   it  is  that  at  Cripple  Creek  we  occasionally  find 


i 


i 


II 


»34 

fragments  of  red  granite  imbedded  in  the  volcanic  breccia 
torn  from  the  throat  of  the  volcano  in  its  passage  through 
the  underlying  granite  of  the  region. 

MINERAL   AND   CHEMICAL    ELEMENTS   OF    LAVAS. 

Eight  chemical  elements  make  up  the  mass  of  lavas, 
oxygen,  silicon,  aluminum,  magnesium,  calcium,  iron,  sodium 
ancl  potassium.  Oxygen  makes  up  the  larger  proportion  so 
that  lavas  are  mostly  oxides.  Next  is  silicon  and  aluminum, 
giving  the  quartz  and  feldspar  and  silicate  element. 

Lavas  are  of  two  kinds,  acidic  and  basic.  Acid  lavas  con- 
tain eighty  per  cent,  silica,  basic  forty-five  per  cent.  The 
former  are  rich  in  potash  and  soda,  the  latter  in  lime  and 
iron;  the  former  are  commonly  light  in  color  and  weight, 
the  latter  dark  and  heavy.  Rhyolite  is  an  example  of  an 
acidic  lava,  basalt  of  a  basic  one.  The  andesites  and  phono- 
lites  ot  Cripple  Creek  are  intermediate.  The  minerals  com- 
posing these  lavas  are  principally  quartz  and  feldspar, 
together  with  the  dark  minerals,  mica,  augite,  hornblende, 
olivine  and  magnetite. 

CRYSTALS   AND    MICROSCOPY   OF    LAVA. 

Many  lavas  are  of  a  glassy  nature,  others  contain  manj' 
crystals,  some  of  large  size. 

Microscopic  sections  of  lavas  show  them  to  be  made  up 
of  a  ground  mass  of  a  glassy  character,  with  distinct  crystals 
set  in  it  like  plums  in  a  pudding. 

In  others,  the  crystals  are  so  thick  that  the  glassy  base 
can  scarcely  be  seen. 

Through  the  midst  of  the  glass,  cloudy  matter  is  observed  ; 
a  higher  power  shows  this  '*  nebula  "  to  be  compc  ^ed  of 
minute  particles  called  crystallites,  the  embryonic  forms  of 
crystals.  Sometimes  we  can  see  an  attempt  of  these  part- 
icles to  aggregate  into  a  geometrical  form,  sketching  out  the 
outline  of  the  large  crvstal  they  intended  to  form,  but  were 
prevented  from  finishing,  by  the  cooling  of  the  glassy 
magma.  These  crystallites  assume  forms  like  ferns,  hairs, 
spiders,  etc. 

In  subterranean  regions  the  conditions  were  particularly 
favorable  for  the  development  of  crystals.  The  lavas  cooled 
with  extreme  slowness,  under  enormous  pressure,  allowing 
plenty  of  time  for  the  crystals  to  form. 

Those  lavas  containing  most  soda  and  potash  (acid  lavas) 
assume  a  glassy  condition,  and  these  have  often  cooled  near 


J35 

the  surface  rapidly,  the  more  crystiiUine  varieties  slowly  at 
great  depth.  Obsidian  and  rhyolites  are  glassy  types,  granite 
and  some  porphyries  with  large  crystals  are  oi  the  latter 
class,  whilst  andesite  and  phonolite  may  be  intermediate. 
The  latter,  however,  at  Cripple  Creek,  may  have  cooled 
quickly  near  the  surface,  and  the  crystals  are  for  the  most 
part  small. 

Besides  the  natural  imprisoned  water,  crystals  in  lavas  are 
found  microscopically  to  contain  globules,  sometimes  filled 


Plate  LXXVIII. 

Minute  Cavities  Containing  Liquids  in  the  Crystals  of  Rock. 

with  gas,  salt,  and  water,  which  may  add  to  the  materials  for 
the  production  of  steam. 

ERUPTIONS  OF  DUST. 

Steam  escapes  from  lava  so  violently  that  the  froth  or 
scum  called  scoria,  is  broken  up  and  scattered  in  all  direc- 
tions. This  scoria  like  pumice  is  full  of  little  holes  like  a 
sponge,  due  to  escape  of  the  steam  in  it.  Such  spongj'  scoria 
is  found  scattered  over  the  hills  of  Cripple  Creek.  During 
violent  eruptions  a  continuous  upward  discharge  of  these 
fragments  is  maintained  ;  the  cindery  masses  hurtling  one 
another  in  the  air,  fall  back  into  the  vent,  or  are  scattered 
over  the  mountain.  Being  often  shot  up  again  and  again 
from  the  vent,  they  are  reduced  to  the  finest  impalpable 
dust.  The)'  fill  the  atmosphere  to  such  an  extent  as  to 
bring  on  an  "  Egyptian  darkness."  This  dust,  mingling  with 
descending  rain,  forms  destructive  mudflows,  and  sets  or 
consolidates  into  the  tufas  or  tuffs  so  abundant  at  Cripple 
Creek.     When  larger  angular  fragments  are  caught  up  and 


? 


136 

consolidated  with  these,  the  rock  so  formed  is  a  breccia,  as 
already  illustrated. 

Volcanic  craters  after  having  been  formed,  are  liable  to 
be  disturbed  by  later  eruptions.  Thus  the  crater  of  Vesuvius 
was  reduced  400  feet  by  a  later  eruption,  the  old  crater  blown 
up  and  a  much  vaster  crater  opened. 

Cripple  Creek  also  witnessed  its  second  disturbance,  after 
the  andestic  eruption  had  ceased,  by  one  of  phonolite  lava. 

FLUIDITY    AND   OTHER    PROPERTIES   OF    LAVAS. 

Some  lavas,  such  as  basalt,  are  reduced  to  such  a  state  of 
fluidity  that  their  streams  run  like  water  to  great  distances. 
Others  are  of  a  more  viscid,  mortar-like  consistence,  espe- 
cially the  acid  lavas,  such  as  those  of  Cripple  Creek.  These 
are  apt  to  flow  but  a  short  distance  from  their  source,  and 
to  build  up  big  domes  and  thick  masses;  of  such  a  nature 
seems  the  structure  of  Nipple  Mountain,  south  of  Cripple 
Creek. 

The  peculiar  columnar  structure  often  observed  in  basaltic 
lava  sheets,  and  in  a  rough  way  developed  in  the  phonolite 
of  the  cliff  above  Victor  mine,  is  due  to  cooling  and  contrac- 
tion somewhat  in  the  same  way  as  mud  cracks  are  formed  in 
a  drying  up  pond.  A  block  of^lava  isolated  by  these  cacks 
assumes  a  polj'^gonal  form  like  the  basaltic  columns  of  the 
Giants  Causeway. 

During  the  cooling  down  of  lava  and  the  escape  of  steam 
and  gases,  deposits  of  sulphur,  specular  iron  ana  (at  Cripple 
Creek)  fluorspar,  are  deposited.  Specular  or  micaceous  iron 
is  not  uncommon  at  Cripple  Creek.  Rock  masses  are  com- 
pletely disguised  by  these  incrustations. 


STRATIFICATION    OF    TUFFS. 

Tufifs  and  breccias  are  often  found  stratified.  The  frag- 
luentary  materials  in  falling  through  the  air  are  sorted,  the 
finer  particles  being  carried  farther  from  the  vent  than  the 
larger  ones.  Craters  built  up  of  tuffs  and  breccias  fallen  in 
the  condition  of  a  muddy  paste,  show  very  fine  stratification. 

Large  cones  are  built  up  of  uniformly  spread  layers  of 
more  or  less  finely  divided  material  disposed  in  parallel 
succession.  At  Cripple  Creek  the  bedding  is  indistinct, 
and  often  difllicult  to  trace,  the  dip  of  stratification  being 
still  more  compressed  by  the  cross  fracturing  of  the  rocks; 
hence  it  is  hard  to  tell  whether  the  lines  represent  cross 


137 


fracture  cleavage,  or  bedding  planes.  In  most  volcanoes 
the  stratified  tuns  are  cut  and  crossed,  as  at  Cripple  Creek, 
by  numerous  dykes  running  in  various  directions,  cracks 
filled  by  lava  from  below. 

Movements,  too,  have  taken  place  subsequent  to  t  le  accu- 
mulation and  consolidation  of  the  whole  material  as  shown 
in  Plate  LXXIX,  whereby  the  masses  are  faulted  and  fresh 
fissures  opened  in  them.  Faults  arc  found  in  some  of  the 
mines  at  Cripple  Creek,  faulting  not  onlv  the  lavas,  but  the 
veins  also.  Cliff  sections  )f  volcanoes  sfiow  alternate  beds 
of  solid  lava,  scoria  and  tuff,  representing  different  eruptions 
or  flows. 

There  seems  an  carder  and  succession  in  the  eruption  of 
the  different  varieties  of  lava.     During  the  earlier  periods 


Plate  LXXIX. 

Cliff  Section,  Composed  of  Alternate  Beds  of  Lava  and  Scoria, 
Cut  by  Lava  Dykes,  and  Faulted. 

rhyolitei:,  andesites  and  phonolites  are  erupted,  and  later 
basalts.  This  appears  to  be  the  case  in  the  volcanic  region 
west  of  Cripple  Creek  around  Mt.  Maclntyre,  Thirty-Nine 
Mile  Mt.,  and  Black  Mt.  The  prevalence  of  basalt  capping 
the  other  lavas  in  that  region,  together  with  the  greater 
freshness  of  the  rocks,  imply  that  its  eruptions  were  some- 
what later  than  those  of  Cripple  Creek  where  basalt  is  not 
found,  and  where  the  rocks  are  much  decomposed. 

Volcanic  eruptions  shift  their  centers  from  time  to  time, 
making  new  cones  along  a  line  of  fissure  (for  volcanoes 
are  built  upon  lines  of  fissure).  See  Plate  LXXX.  Extinct 
craters  are  frequently  filled  by  beautiful  deep  lakes.  Cones 
rise  within  cones,  and  within  great  crater  rings.    At  each 


■3« 

successive  ^^rcat  crupti(in,  the  okl  cone  is  blown  away,  and 
a  new  one  tornicfl. 

Hot  springs  coniain  larj^e  (iiiantitics  of  silica  or  (juart/ 
in  solution.  The  solution  of  silica  is  etk-cterl  at  the  nio- 
ment  of  its  separation  from  combination  with  the  alkali 
duriiifi^  the  decomposition  of  volcanic  rocks,  and  is  lax'ored 
i)y  the  presence  of  alkaline  carbonates  in  the  water,  hif^h 
temperature,  and  the  pressure  under  which  it  exists  in  sub- 
terranean regions.  When  the  water  reaches  the  surface 
and  is  relieved  from  pressure  and  begins  to  cool,  silica  is 
deposited.  So  are  the  basins  of  geysers  formed,  and  so  the 
opal  and  hydrated  quartz  we  find  in  many  oi  the  Cripple 
Creek  veins,  and  in  resilicated  rocks. 

Hot  and  cold  springs  rising  in  volcanic  regions  are 
charged  with  carbonic  acid,  and  passing  through  calcareous 


Plate  LXXX. 

Shoving  Craters  hound  Along  a  Line  of  Fissure  in  tiie  Kruption  of  Etna. 

rocks  dissolve  large  quantities  of  carbonate  of  lime,  and  rc- 
deposit  it  in  a  crystalline  ioriv,  known  as  "  traxertine." 
Near  the  base  of  Mt.  Maclntyre,  west  of  Cripple  Creek,  a 
prospect  is  opened  on  a  fissure  filled  with  this  substance. 

Nearly  all  erupticjns  take  place  along  lines  of  fissures  (See 
Plate  LXXX).  Probably  all  volcanoes  are  located  upon  fis- 
sures of  some  kind,  and  even  the  general  distribution  of  vol- 
canoes over  the  earth's  surface  has  been  ;Utributed  to  lines  (jf 
fissures,  as  if  the  earth  had  been  cracked  like  a  glass  globe. 
We  have  plenty  of  opportunities  of  seeing  ancient  fissures 
filled  with  lava  in  the  numerous  dykes  at  Cripple  Creek, 
and  in  the  greater  volcanic  region  west  of  it;  but  so  far  no 
distinct  volcanic  craters  have  been  found.  Nevertheless  it 
is  probable  that  craters  existed  along  these  fissures,  long 
since  removed  by  erosion,  or  buried  deep  under  flows  and 
surface  matter.  We  not  unfrequently  find  at  Cripple  Creek 
that  fissures  did  not  all  succeed  in  breaking  through  to  the 
surface,  for  at  some  depths  in  the  mines  the  apices  of  buried 


«h5, 


'39 

dykes  are  found  and  fissures  filled  by  vein  nuiUcr,  whose 
outcrops  do  not  appear  at  tiie  surface.  A  single  \ein  is  fol- 
lowed from  the  surface  and  with  depth  two  i)v  more  \eins 
are  often  encountered,  to/^ether  with  various  small  fissures. 
Earth(]uakcs  doubtless  accompanied  the  eruptions,  and 
de\'eloped  many  smaller  fissures,  and  lurther  shattered  the 
rocks.  Added  to  this  at  ("ripple  (reek,  there  was  the  sec- 
ond erupti(jn  of  phonolite,  alter  the  andesite  had  ceased. 
This  second  eruption  doubtless  added  new  lissures  in  the 
efforts  of  imprisoned  vapors  to  f(jrce  for  themselves  chan- 
nels to  tiic  surface. 


(lASKS    AND    SOI.I  AlAKIC    ACTION. 

The  several  staj^es  in  the  decline  of  each  volcanic  out- 
burst are  marked  l)y  the  appearance  at  the  vent  of  certain 
acid  fi;ases.  As  the  temperature  at  the  vent  declines,  t^ie 
nature  of  the  volatile  substances  emitted  undergoes  a 
rej^ular  series  of  chanp^es. 

In  fumaroles,  sulphurtnis  acid  and  hydrochloric  acid 
abound,  with  sulphureted  hydroj^en  and  carbonic  acid  in 
much  smaller  proportions.  Around  these  fumaroles,  de- 
posits of  sulphide  of  arsenic,  chloride  of  iron  and  of  am- 
monia, boracic  acid,  and  sulphur  take  place.  Arsenical 
pyrites  are  a  common  associate  for  the  ores  near  the  sur- 
face at  Cripple  Creek,  and  many  rocks  are  permeated  with 
iron  pyrites. 

Where  a  volcanic  vent  sinks  into  extinction,  hydrochhnic 
and  sulphurous  acids  are  first  evolved,  and  later  sulphur- 
eted hydrogen  and  carbonic  acid  springs.  Such  springs  are 
common  in  the  volcanic  districts  of  Colorado  to-day,  but 
we  have  long  passed  the  stage  of  the  stronger  acids,  which 
could  only  be  expected  in  the  pit  of  an  active  modern  vol- 
cano like  Kilauea.  We  may,  however,  expect  to  find  traces 
left  of  these  gases,  in  the  rocks  of  Cripple  Creek,  such  as 
a  bleaching  and  decoloration  of  the  rocks,  leaching  and 
precipitation  of  iron,  forming  those  varied  patterns  of  oxid- 
ation so  common  at  every  prospect  hole ;  also  deposits  of 
various  sulphates  and  chlorides,  rocks  deprived  of  iron  and 
alkalies  reduced  to  powdery  siliceous  masses. 

One  ;  Jtion  of  subterranean  springs  is  the  transportation 
of  material  in  a  state  of  solution  and  redepositing  of  it 
elsewhere,  especially  in  lines  of  relief  of  pressure,  such  as 
fissures,  shattered  rocks,  and  decomposed  rocks  and  zones 
in  the  rocks. 


I 


! 
I 


C, 


140 

At  Steamboat  Springs,  Nevada,  metallic  golH,  cinnabar 
and  other  minerals  have  been  found  coating  the  sides  of 
fissures  from  which  livinj^  hot  springs  issue  at  the  surface. 
In  f^reat  volcanic  foci  the  transfer  of  various  sulphides, 
oxides  and  salts,  which  fill  veins,  has  been  efTected  either  by 
solution  or  sublimation,  or  the  action  of  powerful  currents. 
This  applies  to  the  veins  and  ore  fleposits  in  cpiestion. 

As  the  ipneous  activity  of  a  district  declines,  the  tem- 
erature  of  the  issuinjj^  ^ases  and  waters  diminishes,  till  at 
ist  the  volcanic  forces  appear  to  have  wholh'  abandoiifd 
the  region  and  been  transferred  to  another.  This  may 
have  been  the  case  with  Cripple  Creek  :uui  the  volcanic 
regi(;n  west  of  it,  of  apparently  later  date.  The  history  of 
a  volcanic  disturbance  is  as  follows: 

First.  The  area  is  troubled  by  subterrariean  shocks  and 
earthquakes. 

Sectind  The  orij^ination  of  fissures  is  indicated  by  the 
appearance  on  the  surface  of  hot  and  carbonic  acid  springs 
and  other  gases. 

Third.  With  increased  subterranean  activity  the  temp- 
erature of  the  springs  and  gases  increases. 

Fourth.     A  visible  rent  is  formed  at  the  surface. 

Fifth.  From  this  fissure,  gas  and  imprisoned  vapor  es- 
capes so  violently  as  to  disperse  the  laxa  in  clouds  of  scorir* 
or  dust,  or  to  cause  it  to  well  out  in  flows. 

Sixth.  Volcanic  action  concentrates  at  one  or  several 
points,  and  the  ejected  material  accumulates  from  volcanic 
cones. 

Sometimes  the  volcanic  activity  dies  out  entirely,  leaving 
cones  thrown  up  along  the  line  of  fissure.  At  others,  some 
such  center  becomes  for  a  long  time  the  habitual  vent  for  the 
volcanic  forces  of  the  district,  and  a  large  cone  is  built  up. 

When  the  height  and  thickness  of  the  cone  have  grown 
great,  the  succeeding  eruption  rends  the  sides  of  the  cone, 
producing  fissures,  quickly  filled  by  'ava.  forming  radiating 
dykes  and  surmounted  by  parasitic  cones.  The  dykes  of 
Cripple  Creek  may  in  cases  represent  such  occurrences. 

when  volcanic  energies  can  no  longer  raise  material  to 
the  summit  of  the  crater,  nor  rend  the  sides,  they  find  relief 
by  making  new  fissures  and  small  cones  in  the  country  out- 
side the  main  volcanic  crater.  The  numerous  phonolitic 
dykes  in  the  granitic  region  outside  of  the  main  center  at 
Cripple  Creek  may  have  so  originated.  At  last  volcanic 
energy  diminishes,  eruptions  of  lava  cease,  fissures  are 
sealed  up  with  solid  lava,  volcanic  cones  crumble  away. 


141 

Hut  still  the  existence  •>!  heated  matter  at  no  j^ieat  deptfw 
is  indicated  by  outbnists  of  ^^uses  and  vapor,  lorination  of 
jj[eysers,  mud  volcanoes  and  hot  sprinjj^s.  As  tlie  underlying 
rocks  cool  down,  the  issuinjr  jets  <»!  jj^as  and  \apor  lose  their 
liijjfh  temperature,  diminisli  in  (piantity,  ^^eysers  and  inurt 
volcanoes  become  extinct,  IkH  springs  disappear,  and  all  is- 
(piiet. 

It  was  in  the  latter  or  hot  sprinjj;  staj^e.that  the  ores  were 
at  Cripple  Creek  leached  from  the  volcanic  rocks,  probably 
frcjin  f^reat   depths  as  well   possibly  as   from  the  sides,  and 
concentrated  and  deposited  in  the  fissures,  shattered  zones,, 
and  decomposed  rocKs.     The  last  staj^e  is  as  we  find  thinj^s. 
t<j-day. 


r.r.NKRAL   SUMM.\RV   OF     I'ROI'.ARI.K    VOLCANIC    KVENTS    IHAl 
OCCUKRF.D    AT   Ck!l'IM.K   CKKKK. 


At  Cripple  Creek  there  was  a  volcanic  eruiition  in  T»,'rti- 
ary  times  due  probably  t<j  some  mountain  elevation  f,'oinjr 
on  in  the  rejj;ion  of  Pike's  Peak  or  j>enerally  in  the  moun- 
tains. 

We  may  assun'C  that  preludinj,^  the  eruption  the  area  was- 
troubled   by  eartlupiakes.     Various  kinds  of  acid  and  hot 
sprinj^s  appeared  above  the  surface,  indicating  the  tissuring 
of  the  ground  that  followed. 

At  the  bottom  of  ibese  fractures,  which  may  have  beeni 
numerous,  molten  rock  appeared,  giving  otT  imprisoned 
vapor  from  bursting  blisters  of  lava.  These  shoots  (jf  steam; 
formed  into  a  cloud  overshadowing  the  area,  and  carried 
upwards  quantities  of  scoria  and  fragments,  which  fell  back 
around  the  orifices,  forming  ;»  crater  cone,  or  craters.  These 
fragments  being  repeated!-  s)  )t  up,  and  falling  back  into- 
the  crater  were  comminuted  into  tine  dust,  and  fell,  together 
with  larger  angular  fragments,  ovcv  the  surface. 

The  atmosphere  charged  w/h  condensing  stenmgave  rise- 
to  heavy  rain  falls.  The  w..tcr  descending  the  ravines,, 
caught  up  the  volcanic  dust  and  fragments,  forming  mud- 
flows,  the  materia!  rapidly  setting  into  the  rocks  we  call 
tufa's  and  breccias. 

As  tlie  first  eruption  at  Cripple  Creek  was  of  andesite, 
these  are  called  andesitic  tuffs  and  breccias,  and  constitute 
the  principal  mineralized  rock  of  the  mining  area. 

These  tutTs  are  sometimes  stratified  by  the  materials  be- 
ing sorted  in  the  air  by  the  water. 

After  this  lirst  eruption  ceased,  there  may  have  been  a 


I 

I 


H2 

rest  for  a  time,  the  lavas  may  have  cooled  and  ccnisolidated, 
and  the  region  been  covered  by  xarious  acid  and  hot 
springs,  issuing  from  fissures  caused  by  tiie  late  eruption. 

Then  the  district  was  a  second  time  disturbed,  this  time 
by  an  eruption  of  phonolite,  ascending  thnjugh  numerous 
rents  and  fissures,  not  only  in  the  overlying  andesite,  but 
also  in  the  granitic  region  outside  of  the  first  volcanic 
"focus,"  probably  finding  the  old  seat  of  action  too  much 
choked  by  eruptive  matter. 

This  second  eruption  added  many  new  fissures  to  the  al- 
ready shattered  rocks,  and  gave  many  opportunities  for  the 
deposition  of  metallic  and  \'ein  material  deposited  through 
the  medium  of  -^aseous  and  hot  spring  and  solfataric  actioi' 
which  followeci  upon  the  cessation  of  the  phonolite  erup- 
tion. 

After  the  eruptions  at  Cripple  Creek  ceased  the  volcanic 
forces  seem  to  have  transferred  their  field  of  action  to  the 
area  west  oi  Cripple  Creek  in  the  Four-mile  district.  The 
rest  is  the  history  of  to-dav. 


CRIPPLK   CRKEK    AS    A    l'ROSPl<:C  lINd    FIKLD. 

A  visitor  standing  on  top  of  one  of  the  hills  like  Mt. 
Pisgah,  overlooking  Cripple  Creek,  and  glancing  at  the 
various  mines  and  multitudinous  prospect  holes  speckling 
the  hills,  is  struck  with  the  compactness  of  the  mining  dis- 
trict within  the  limited  area  of  18  square  miles.  In  this 
small  area  all  the  principal  mines  are  located,  and  one  can 
ride  arcjund  the  ent'.e  camp  in  an  htnir  (jr  two.  Outside  of 
this  area,  there  are  as  yet  no  mines  of  importance,  though 
prospect  holes  may  be  found  for  a  circuit  of  many  miles. 


i 
I 


ANDKSITIC   AND   GRANITE   AREAS. 

He  will  observe  that  the  principal  mines  are  located  on 
the  round  smooth  hills,  on  their  tops,  slopes  and  on  the 
gulches,  where  the  vegetation  is  mostly  grass  and  quaking 
aspen.  These  too  are  within  a  sort  o'f  natural  rampart  of 
more  rugged  hills  wooded  with  pine.  In  these  outlying 
hills,  only  a  few  scattered  prospects  are  visible.  The  reason 
for  this  is  to  be  found  in  the  geology  of  the  region,  and  the 
dififerences  between  the  areas  occupied  l)y  andesitic  breccia 
and  granite.  The  rounded  grassy  aspen-covered  hills  re- 
presenting the  andesitic  brecria  carry  most  of  the  ore 
bodies,  and  the  principal  mines  are  restricted  to  them.    The 


143 

more   ruf?f?ed   hills,  covered   with    tir  trees,    represent   the 
jjranite  area,  and  in  them  for  the   most  part  are   few  mines 
(jf  importance,  though   many  hkely  prospects  are  opened 
upon  dykes  of  phonoMte,  which,  so  far  as  known,  does  nc 
as  a  rule  seem  to  be  so  productive  a  rock  as  the  andesite. 

There  are  intermediate  areas,  such  as  that  of  Battle  Mt., 
characterized  by  the  presence  of  both  andesitic  breccia,^ 
phonolite  dykes,  and  granite,  in  which  are  some  of  the 
richest  mines  of  the  district,  such  as  the  Independence, 
Portland,  Annie  Lee  and  others. 

It  will  appear  how  important  and  useful  a  ge(jIogica{ 
survey  is  oi  such  a  region,  a  fact  not  always  recognized  by 
practical  miners.  If  the  ore  bodies  are  mainly  associated 
with  the  particular  rock  called  andesitic  breccia,  it  is  well 
for  them  to  be  able  to  recognize  that  rock,  and  ascertain 
the  limits  of  its  area. 

SIGNS   THAT    LEAD   TO    PROSPF.CTINO. 

The  next  thing  that  strikes  the  observer,  is  the  prodig- 
ious amount  of  prospecting  holes  and  prospecting  trenches, 
the  latter  being  particularly  common.  lie  may  ask,  what 
was  there  in  the  general  appearance  and  character  of  this 
district  that  led  the  "  eagle  eyed  "  prospector  to  suspect  the 
existence  of  ore  bodies  in  it,  or  that  it  was  "a  kinder 
likely  locjking  place".''  Again,  how  is  it  that  it  was  so  long 
overlooked  by  the  "  eagle  eyed,"  especially  when  so  easily 
accessible  ? 

On  general  principles,  in  past  years,  miners  in  Colorado, 
after  the  Leadville  and  Aspen  excitement,  were  more  on 
the  lookout  for  silver  than  gold  ;  they  locjked  therefore  for 
rocks  like  those  of  Leadville,  with  contacts  between  por- 
phyry and  limestone,  and  e\'ery  limestone  ledge  in  the 
country  was  ransacked.  Silver  was  rarely  found  in  xolcanic 
lava  rocks,  except  perhaps  in  the  great  San  juan  region, 
and  miners  thcmght  as  little  about  prospecting  unpromising 
looking  hills  of  lava,  as  they  would  the  Ixisaltic  caps  of  the 
table  mountains  on  the  plains.  Again,  gold  leads  do  not 
show  their  ore  on  the  surface  like  some  silver-lead  \-eins. 
There  is  nothing  perhaps  but  a  little  seam  of  rust  that 
might  occur  almost  anywhere,  and  in  any  kind  of  rock. 
Hence  lava  districts  of  somewhat  recent  origin,  were  oxer- 
looked,  rather  than  looked  over.  The  discovery  of  the 
gold-bearing  properties  oi  the  Cripple  Creek  lavas,  together 
with  the   increased  thirst  for  gold,  turned  the  tables,  and 


1l 


t    1 


144 

mow  iTiroughout  Colorado,  every  lava  formation  is  being 
rprogpected  with  as  much  zeal  and  mdiscriniinateness,  as 
\were  ihe  limestones  in  the  Leadville  days.  The  prospector 
maw  needs  to  know  volcanic  lavas  at  sight,  to  distinguish 
'.varieties,   and    to  know    all  he   possibly  can   about   their 

•  origin,  varieties  and  mode  of  occurrence.  Hence  the  im- 
iportance  we  gave  to  the  subject  in  the  preceeding  remarks 
»on  volcanoes.     A  prospector  n<nu  would  at  a  glance  con- 

siderlhe  area  about  Cripple  Creek  as  worth  looking  over; 
.and  the  geologist  woula  consider  it  a  very  likely  place,  not 

unerely  from  the  presence  of  the  lavas,  but  mainly  from  the 
rgreat  decomposition  of  the  rocks,  and  the  evidence  of  the 
presence  of  past  solfataric  action. 

DIFFICULTIES   IN    PROSPECTING. 

But  the  '*  eagle  eyed  "  one  did  not  entirely  overlook  this 
•district  in  the  past,  for  some  years  ago  he  was  sufficiently 
prepossessed    with   the   appearance   of   things  to   drive   a 
couple  of  short  tunnels  in  Arequa  gulch,  and  narrowly  es- 
«caped  becoming  a   millionaire.      What  troubled  the  pros- 
pector was,  that  though  he  found  the  hills  covered  with  an 

•  extraordinary  amount  of  "float,"  he  could  not  trace  this 
float  to  any  ledge  or  rocks  "  in  place."  For  the  most  part 
the  hills  were  grassed  over,  or  covered  with  vegetation  ;  and 
through  the  turf  were  very  few  outcroppings  of  a  likely 
kind,  so  far  as  he   could   see.     There  were    no   prominent 

•  quartz  veins,  or  zones  deeply  impregnated  with  iron,  hence 
he  gave  up  the  region,  mentally  wondering  where  on  earth 
all  this  rich  float  could  have  come  from,  perhaps  solacing 
his  mind  by  one  of  his  igneous,  brimstony  theories  that  it 
;had  been  scattered  over  the  country  from  a  distant  volcano, 
•or  washed  there  by  flood  or  glaciers  from  some  unknown 
distant  region.  The  former  theory  after  all  was  not  far 
from  the  truth  but  the  absence  of  all  rounding  and  smooth- 
ing of  the  fragments  of  float  precludes  the  latter  hypoth- 
■esis.  Evidences  of  former  glaciation  are  remarkably 
absent  from  the  vicinity. 


THE   REGION    IMPREGNATED    WITH    ORE. 

To  those  who  have  studied  Cripple  Creek  of  to-day,  the 

•source  of  this  "  float  "  is  no  mystery.      Little,  if  any  of  it, 

has  been  broken  ofT  from  orthodox  quartz  fissure  veins,  or 

•  even  extracted  from  well  defined  ore  zones.     The  fact  is. 


145 

that  the  whole  andesitic  area  is  more  or  less  impregnated 
with  the  precious  metals,  and  the  float  on  the  surface  is 
little  more  than  the  surface  debris  of  the  general  underly- 
ing rock.  There  is  scarcely  a  stone  that  you  may  kick  with 
your  foot  over  the  entire  area,  but  what  will  show  some 
trace  of  gold,  On  one  hill  an  experieiiced  mining  superin- 
tendent told  me,  that  for  an  experiment,  he  went  around 
with  a  wagon  and  picked  up  the  "float"  almost  at  hap- 
hazard, and  it  averaged  22  dollars  m  gold.  That  such  a 
*'  floaty  "  region  should  receive  attention  some  day  is  not  to 
be  wondered  at,  and  we  believe  Colorado  Springs  men  were 
amongst  the  first  to  give  it  serious  attention  by  opening 
holes  and  prospecting  trenches  almost  at  random,  result- 
ing in  important  discoveries.  As  a  rule  even  after  this,  the 
best  mines  were  discovered  by  mere  chance  and  {.niess 
work,  or  by  plodding  but  blind  prospecting,  s(jmeti)ing 
like  the  Leadville  prospector  who  in  early  days  had  all 
Leadville  before  him  to  prospect,  but  did  not  know  where 
to  begin,  till  sitting  down  under  a  tree  eating  his  lunch,  he 
saw  a  squirrel  scratching  in  the  ground  ;  he  accepted  the 
happy  omen  and  "went  dovvn,"  so  the  story  goe?:  and  o' 
course  "struck  it  rich;"  so  we  understand  the  Pharnnicist 
and  many  other  now  noted  mines  were  discovered  atCri[)ple 
Creek. 

MODE  OF    PROSPECTING. 

This  absence  of  surface  outcrops  or  visible  leads,  when 
the  "  rush  "  came,  led  to  indiscriminate  and  abundant 
[jrospecting  which  has  been  kept  up  till  the  present  time, 
lience,  the  extraordinary  freckling  of  the  hills  with  prospect 
holes  and  trenches. 

Sometimes  the"  would  select  any  piece  of  land  they 
thought,  for  some  reason  01  other  or  without  any  reason 
at  all,  likely,  and  go  to  work  to  punch  holes  and  dig 
trenches  all  over  it  to  find  something.  In  this  way  they 
frequently  came  across  enough  signs  to  warrant  putting 
down  a  prospect  hole,  and  holding  the  claim  and  then  went 
on  "  to  pastures  new." 


CHARACTER  OF    FLOAT    AND   OTHER   SURFACE   SIGNS. 

As  we  have  said,  the  whole  region  is  covered  with  float. 
This  float  is  usually  a  somewhat  porous  piece  of  hwa,  or 
andesitic  breccia,  or  tuflf,  stained  with  yellow,  brown,  or  red 
oxide  of  iron,  sometimes  in  patterns  or  concentric  rings.    It 


146 

is  often  found  to  be  honeycombed  when  broken  with  a 
hammer.  There  is  no  visible  ore,  but  an  assay  will  most 
likely  show  traces  of  more  or  less  go\(\.     Ajj^ain,  a  species  of 


ill 


red  porphyritic  granite  has  been  dcsilicaicd  and  robbed  <»f 
many  of  its  crystal  constituents,  and  left  ;is  a  porous  skeleton 
of  a  rock  by  the  action  of  j^ases  and  sprinj^s.  The  jjores  in 
this  are  often  occupied  by  oxide  of  iron,  or  even  by  crystals 


i 

I 


L 


147 


i)f  fluorspar.  This  is  a  likely  kind  of  float,  lloneycombcfl 
rusty  rock  with  fjuartz  crystals  is  a  likely  float,  both  of  these 
representing  the  action  of  mineral  hot  sprin<rs.  At  rare 
intervals  we  may  see  a  little  of  this  oxidized  rusty  rock  in 
place  protrudinj^  from  under  the  grass,  and  if  so,  there  is 
sure  to  be  a  prospect  hole  alongside  of  it. 

Bold  outcrops  of  lava  rock  are  comparatively  scarce  and 
when  they  do  appear,  as  in  the  cliff  above  Victor  mine,  Mt. 
Pisgah,  Bahr,  and  Rhyolite  peaks,  the  rock  is  apt  to  be  s(i 
hard  as  to  preclude  the  probability  of  much  ore  deposits 
in  it. 

Pieces  of  rock  or  float  stained  a  \i(jlet  purple  color  by 
fluorine  are  considered  a  good  sign  of  an  ore  body  not  far 
otT,  this  fluorspar  being  found  characteristic  of  some  of  the 
richest  veins  in  the  camp  ;  and  flu(jrine  gas  was  dcjubtless 
connected  with  the  deposits  of  ore  matter,  especially  oi  t:.e 
tellurium,  the  present  matrix  of  the  gold  in  the  deeper  parts 
of  the  mines. 

Pyrites  is  not  usually  found  on  the  surface  till  the  rock 
is  broken  open,  and  tellurium  in  little  silver  scales  and  spots, 
not  till  C(jnsiderable  depth  is  attained.  But  free  gold  may 
be  found  in  surface  float,  and  from  the  grass  roots  down, 
and  in  the  early  development  of  a  mine,  in  the  oxidized 
upper  portions,  associated  with  iron  oxide  and  black  man- 
ganese or  "  psilomelane." 

Micaceous  or  specular  iron,  is  seen  in  some  prospect 
holes  ;  and  localities  marked  by  evidences  of  past  h<jt  spring 
action,  such  as  the  appearance  of  botryoidal  chalcedony  or 
opal  should  be  prospected.  A  common  and  curious  marking 
in  some  of  the  bleached  volcanic  lavas  is  that  of  an  imitation 
of  trees,  ferns  and  mosses,  popularly  called  "  photographic 
rock,"  scientifically  "  dendrite  "  or  tree  rock. 

This  remarkable  imitati(jn  of  nature  is  due  to  crystalliza- 
tion of  solutions  of  manganese,  and  may  be  compared  to 
fern-like  appearances  on  a  frosty  window-pane  in  winter, 
which  are  certainly  not  of  organic  origin,  or  in  anj'way  con- 
nected with  the  processes  of  photography.  These  dendritic 
markings  may  or  may  not  be  considered  as  signs  of  ore. 
Similar  markings  are  very  common  in  the  porphyries  of 
Leadville  overlying  the  silver  deposits. 


V      i 


SURFACE   PROSPECriNG   OF   A    MINE. 

In  some  of  the  surface  discoveries  of  mines,  when  a  con- 
siderable  area,   covered   by   a   blow-out  of   iron   oxide  as- 


148 


I  1 


m 


*'.i 


:•** ' 


i 


sociated  or  not  with  purple  fluorspar,  has  been  found  to  run 
well  in  free  jjoid,  the  ji^njund  is  prospected  and  developed  to 
the  depth  of  a  few  feet,  and  (j\er  a  certain  area,  with  nhjws 
and  scrapers,  the  material  so  obtaijicfl  heinj^  sent  wholesale 
to  the  stamp-mill  and  often  K^'ving-  rich  returns.  The  (object 
of  this  work  i-,  not  mereh'  to  get  all  the  values  out  of  this 
rich  float,  but  in  hopes  of  uncovering  the  vein  or  veins  of 
which  it  is  the  oxidized  cap  or  blossom.  This  was  the  way 
in  which  the  Deerhorn  mine  was  opened  up,  and  its  xeins 
fliscovered  on  Summit  Hill,  The  ground  on  the  top  of  the 
hill  is  observed  to  have  been  "gophered"  in  all  directions 
like  the  catacombs  to  a  depth  of  about  20  feet,  and  over  an 
area  of  a  square  acre  or  so.  This  was  done  partly  to  gather 
up  and  collect  the  rich  float  which  was  found  scattered  o\er 
the  hill  and  partly  to  discover  the  leads  in  place. 

This  rich  float  was  stained  with  purple  fluorine,  and  up- 
wards of  25,000  dollars'  worth  of  gold  was  obtained  from 
this,  the  material  being  dug  up  by  plows  and  scrapers,  be- 
fore the  subsequently  discovered  veins  were  found  or 
worked. 

In  the  case  of  the  Anaconda  mine  on  Gold  Hill,  the  out- 
crop of  a  dyke  of  andesite  was  discovered  on  the  hillside 
covered  with  an  o.xidzed  crust  carrying  gold.  The  owners 
developed  this  by  an  open  quarry,  about  a  hundred  feet  in 
length  and  40  to  50  feet  deep,  from  which  they  extracted 
the  bonanza  wiiich  made  this  mine  at  its  outset  so  cele- 
brated, and  later  proceeded  to  uncover  the  dyke  on  the 
surface,  to  a  depth  of  about  30  feet  along  the  entire  length 
of  their  claiins,  but  nothing  comparable  with  the  bonanzas 
of  the  first  quarry  has  been  found  since  in  extension  or 
depth. 

RICHNKSS   WITH    DEPTH,    KTC. 

Many  of  the  mines  shipped  their  best  ore  from  the  grass 
roots  and  upper  /xidized  portions  of  the  veins,  which  con- 
tained free  gold  u.nd  were  free  milling.  With  depth  some  of 
these  mines  havf  not  done  nearly  as  well,  especially  when 
they  reached  the  unoxidized  zone,  away  from  surface  in- 
fluences, and  the  ore  was  found  wrapped  up  in  tellurium  or 
iron  pyrites. 

The  palmiest  days  of  many  a  gold  camp  arc  its  earliest 
days. 

SUCGESTION.S   TO    PROSPECTORS. 

In  the  more  productive  area  the  prospector  will  do  well 
to  keep  to  the  andesitic  breccia,  and  follow  the  sii;>is  we 


s 


149 

have  mentionefl.  Outside  of  this  area  his  course  may  be  a 
little  different,  as  then  he  is  in  the  granite  district,  and  looks 
out  for  the  appearance  of  dykes  of  phonolite,  rarely  more  than 
a  few  feet,  though  sometimes  many  yards,  in  width,  and 
easily  distinguished  from  the  red  granite  by  their  light  gray 
or  white  C(jl(jr.  These  dykes  do  not  often  appear  out- 
cropping in  the  granite  cliffs,  but  are  more  commonly  t(;  be 
found  buried  beneath  the  debris  and  grass  oi  the  slopes. 
On  these  he  may  find  n(;  indication  and  trust  to  haphazard 
trenching;  or  a  few  stray  pieces  may  lead  him  to  the  spcjt. 
The  more  rusty,  oxidized  and  decomposed  the  phonolite, 
the  more  likely  it  is  to  carry  gold  ;  at  times  he  may  find  ore 


Platk  LXXXII. 

ection  Mooss  Mine  Veil),  Raven  Hill.  i.  Country  Rock  Breccia.  ?.  Yellow 
Jasner,  with  Cavities  of  _  (Quartz  Crystals.  3.  Blue  Grey  Jasper,  with  Seams 
of  'juartz  and  Iron  containing  Gold. 

and  iVee  gold  in  the  dyke  itself,  but  more  often  at  its  con- 
tact, on  (jne  or  both  sides,  with  the  granite.  There  he  is 
likely  to  find  a  crevice  filled  with  clay  or  iron-oxide,  carry- 
ing seams  and  cavities  lined  with  quartz  crystals  or  stains 
(jf  purple  fluorspar, 

S(jmetimes  he  may  find  the  coarse  granite,  as  in  the  case 
of  the  Independence  mine  <jn  Battle  Mt.,  just  at  the  contact 
with  the  dyke  of  lava,  to  be  very  rotten,  much  honeycombed 
and  robbed  of  many  constituent  minerals,  and  these,  by  re- 
placemer.t  with  metal,  may  yield  him  the  richest  ore. 
Again,  the  dyke  between  walls  may  be  reduced  to  a  blue  or 
yellow  jaspery  clay,  with  a  \ertical  lamination  or  cieav^age, 
the  lines  of  cleavage  filled  Avith  tjuartz  and  iron  oxide 
(See  Plate  LXXXII);  in  such  lines  he  is  apt  to  find  the 
richest  ore. 


ISO 


After  opening  a  prospect,  tlie  (^re  signs,  consisting  of 
stains  of  oxide  of  iron  and  manganese,  instead  of  pursuing 
an  even  or  regular  course  are  apt  to  scatter  amongst  the 
infinite  number  of  crevices  shattering  tiie  rcjcks,  no  one 
little  lead  being  of  sufficient  richness  to  f(jllo\v  with  profit, 
and  the  whole  body  between  walls  scarcely  paying  to  work. 

The  ore  signs  often  follow  a  very  uneven  course,  now 
lying  upon  a  fairly  defined  wall,  then  running  for  a  distance 
into  one  wall  or  other,  or  again  following  the  main  C(jurse 
of  the  creviced  lava  breccia  between  walls,  now  in  pockets 
and  crevices,  again  scattered,  or  again  impregnating  the 
ponjus  and  decomposed  rock.  There  are  very  few  true, 
well-defined  veins  in  the  camp;  the  ore  rather  impregnates 
certain  ill-defined,  shattered  zones  of  rocks  between  certain 
ill-defined  boundaries  called  walls.    At  others  the  ore  occ.i- 

Eies  narrow  cleavage  planes  in  the  rock,  of  which  there  may 
e  two  (jr  three  in  a  mine,  some  of  them  productive,  others 
very  little  so.  Ore  bodies  in  the  harder  or  more  compact 
rocks,  such  as  the  Buena  Vista  and  Victor  mines,  are  apt  ti> 
have  something  more  like  defined  veins  and  defined  walls. 
In  some  cases  surface  signs  have  been  poor,  and  with  depth 
have  done  well ;  the  exact  opposite  has  often  been  the  case. 
Some  mines  have  been  good  from  bottom  to  top,  but  we 
have  to  be  careful  here,  as  in  most  gold  camps,  of  the  old 
fallacy  of  "  richness  with  depth."  There  is  little  more 
criterion  for  this  than  in  other  camps,  and  many  a  once 
famous  mine  is  looking  vainly  with  depth  for  its  lost 
bonanza,  though  in  other  respects  doing  fairly  well. 

As  regards  the  granite  itself,  we  have  heard  of  few  (ordi- 
nary quartz  fissure  veins  unaccompanied  by  lava  intrusions 
proving  productive. 

The  fine  grained,  red,  eruptive  granite  on  Barnard  Creek, 
north  of  Cripple  Creek,  has  shown  a  promising  ore  body  in 
a  lava  dyke  in  the  granite,  which,  singularly  enough,  i)ro- 
duces  a  fine  grained  galena,  rich  in  gold.  Galena  is  quite  a 
rare  ore  in  Cripple  Creek.  Green  carbonate  of  copper 
stains  appear  at  times  in  the  schists  and  gneisses,  but  none 
so  far  productive. 

The  railroad  from  Canyon  City  to  Cripple  Creek  did  s(jme 
good  prospecting  work  in  the  granite  area,  its  cuttings 
exposing  quite  a  number  of  ph<jnolite  and  other  dykes, 
together  with  some  granitic  veins. 

Outside  of  Cripple  Creek,  in  the  great  volcanic  area  to 
the  north,  between  Cripple  Creek  and  South  Park,  is  a  fair 
prospecting  field.    The  rocks  are  mainly  granites,  rhyolites, 


......^^.mmmmmm 


»5i 

trachytes,  andcsitcs  and  basalt,  the   products,  as  at  Cripple 
Creek,  of  a  series  of  vcjicanic  eruptions,  cjf  wiiicii  the  latest 


\: 


appears  to  have  been  basalt,  wliich  conmionly  caps  tlie 
Dther  and  h^hter  cohjred  lavas. 

The  rocks  in  this  region  are  for  the  most  part  less  decom- 
posed than  those  at  Cripple  Creek,  whicii  is  not  so  favorable 
a  sig".  Here  the  prosjiector  should  look  out  for  all  sijj^ns 
of  decompositi(jn.  such  as  we  (observed  at  Freshwater  dis- 
trict, a  not  upl'kely  spot.  The  very  hard,  massive  rocks 
are  not  likely  to  be  pr(Kli!Cti\'e.  such  as  the  iiard  black 
basalts.  The  lifj^hter  coI<Med  and  more  decomp(jsable  la\as 
offer  a  better  chance. 

(^enters  of  eruption,  such  as  relics  of  old  craters  and 
flykes  from  which  these  ditlerent  lavas  issued,  shovdd  be 
soujj^ht  for  and  prospected.  Balfour,  a  small  mininff  camp 
at  the  north  of  this  area,  is  established  amc^nji^  ji^ranite  and 
eruptive  rocks,  which  have  been  found  Uj  be  minerali/efl 
by  pyrites.  The  jj^ranites  here  have  several  fissure  \eins 
anfl  dykes  in  them,  showing  considerable  disturbance  to 
have  taken  j)lace  in  that  neighborhood.  The  low  hills  in 
whicli  the  prospect  holes  arc  located  are  capped  with  basalt, 
a|iparentl\'  resting  on  volcanic  tufTs  and  other  la\as.  So 
far.  n(jthing  very  productive  has  been  lound,  though  here, 
as  elsewhere,  much  is  h(jped  for  with  depth.  Singularly 
enough,  in  one  of  these  veins  in  lava,  we  noticed  a  tarry 
substance  or  inspissated  bituir.^n  in  the  cavities  of  the  rock, 
an  unusual  occurrence  in  fissure  veins  or  in  volcanic  rock. 


CHAPTKR   XII. 
ORE  DEPOSITS  IX  SEDIMENTARY  ROCKS. 


I'.I.ANKKT   OKK    DKHOSITS.   CONTACT    I^KI'OSITS. 

This  great  second  class  of  ore  deposits,  occurring  princi- 
pally in  Paleozoic  limestones  at  contact  more  or  less  with 
intrusive  sheet!?  of  porphyry,  is  mainly  represented  in 
Colorado  by  the  Leadville  and  South  Park  mining  district, 
the  Kokomo  and  Red  ClilT  districts,  and  the  Aspen  and 
(iunnison  districts,  though  hjcally  here  and  there,  wherever 
PaleoZ(MC  strata  accompanied  by  igneous  rock  m  ly  be  ex- 
posed, sih'er  mines  may  be  found.  We  will  begin  with  Lead- 
ville and  Scjuth  Park  as  primarily  instructix'e  and  typical. 


i 


f 


152 

SOUTH    PARK    OKK    DKroSM'S. 

The  basin  plain  of  South  Park  is  underlaid  by  sedimentary 
rocks  from  the  Cambrian  below,  to  the  Upper  Cretaceous 
on  top.  These  strata  slope  up  to  the  crest  of  the  Moscjuito 
ranpe  on  the  west,  where  they  become  violently  folded  and 
faulted  and  eroded. 

The  miricral  developments  are  on  the  slopes  of  this  range 
on  both  sides  of  it. 

The  (jrder  of  succession  of  strata  forming  the  structure 

>jffi^i*!;Q^^^~i:^5^!^^^^^^  Di-ah  flolofnitio 
y^V^^>?*^^S^^5S^^^^^?^  Cnmhrtttn 

Platf.  LXXXIII. 

Section  of  Lcadville  Cliff. 

and  cliffs  of  the  range  and  resting  on  the  granite,  is  as  fol- 
lows, beginning  with  the  lowest : 

Feet  tliick. 

Cambrian  quartzite aoo 

Silurian  drab  limestone  (dolomite) zoo 

Lower  Carboniferous  blue  limestone aoo 

Middle  Carboniferous  sandstones  and  (|uartzitc  (Weber  grits).  .2,000 
Upper  Carboniferous  limestones,  reddish  sandstones 1,000 

Total 3,600  to  4,000 

These  formations  have  been  traversed  by  eruptive  quartz- 
porphyry  and  porphyrite  dykes  and  intrusive  sheets.  The 
dykes  occur  principally  in  the  Archa?an,  but  the  intrusixe 
sheets  are  many  and  are  spread  out  between  the  quartzites 
and  limestones  of  the  Cambrian,  Silurian  and  Carboniferous. 


■^SCRS? 


153 

The  connection  bctwc>'n  the  eruptive  masses  and  deposition  of 
ore  is  very  marked.  The  ore  bodies  are  a  concentration  of 
the  metallic  minerals  oriji[inalIy  Hisseminated  throufj^li  the 
mass  of  these  eruptive  porphyries  and  deposited  alonjj;  their 
plane  of  contact  with  the  sedimentary  beds,  and  by  metaso- 
ni.itic  substitution  extending  more  of  less  into  the  mass  of 
the  latter. 

On  mountains  Lincoln  and  Bross,  in  the  principal  mines, 
the  ores  are  mainly  argentifennis,  yielding  galena  and 
its  products  of  decomposition,  vi/.,  carbonate  of  lead 
(cerussite)  and  sulphate  of  lead  (anglesite)  with  chloride  of 
silver.  Barite  (heavy  spar)  is  a  common  gangue  (jr  vein- 
stone especially  in  the  richest  parts  of  tlie  mine.  Iron 
pyrites  ciecomposed  and  passing  into  a  hydrated  o.xide  of 
iron,  together  with  a  black  o.xide  of  manganese,  give  to  the 
ore  its  rusty  and  black  color. 

The  deposits  occur  in  irregular  bodies  or  pockets  often  of 
great  size,  in  the  blue  limestone,  near  its  upper  surfa  ,e,  but 
not  always  easy  to  find  or  follow.  This  limestone  was 
originally  covered  by  a  sheet  of  (piartz-porphyry  which  has 
been  locally  removed  from  the  ore  deposits,  but  e.xists  in 
the  peak.  This  porphyrv,  generally  recognized  by  its  large 
feldspar  crystals  is  calleH  Mt.  Lincoln  porphyry  and  is  quite 
common  and  characteristic  of  Western  Colorado.  In  the 
Dolly  Varden  mine  the  ore  occurs  in  the  limestone  at  con- 
tact with  a  7'ertiial  dyke  of  white  (juartz-porp/iyry. 

In  the  Kanny  Barrett  mine,  on  Loveland  Hill,  rich  deposits 
of  galena  and  anglesite  occur  in  a  vertical  tissure  (probably 
a  gash  vein)  crossing  the  hill  from  side  to  side  and  travers- 
ing the  Paleozoic  strata  at  right  angles  to  their  dip,  but 
probably  not  entering  into  the  underlving  granite.  This 
mine  was  discovered  by  nt^ticing  little  pfeces  of  iron  f(jllow- 
ing  a  general  line  across  the  hill. 

In  Buckskin  Gulch  the  Phillips  mine  is  an  immense  mass 
of  gold-bearing  iron  pyrites,  deposited,  in  beds  of  Cambrian 
quartzite  near  a  dyke  of  quartz-porphyry.  This  mine  was  dis- 
covered by  its  rusty  outcrop  being  exposed  along  the  edge 
of  the  stream.  At  first  this  crust  of  iron  o.xide  was  hjose 
enough  to  be  panned  for  gold  with  good  success  by  the  old 
timers,  and  afterward  milled.  But  when  the  hard  pyrite  set 
in,  the  ore  was  found  to  be  too  low  grade  to  pay  for  roasting 
and  smelting,  and  for  many  years  lay  idle.  The  Criterion  in 
the  cliff  above  this  consists  of  Iari;^e  caves  in  Cambrian  (piart- 
zite,  still  partly  occupied  by  o.  idized  gold-bearing  iron  ore, 
and  galena-bearing  silver  c/ose  to  a  porphyrite  dyke. 


m 


'54 

The  Loiuloti  mine  in  Mi)sr|uit<)  «:ulcli  is  peculiar  and 
instructive  as  beinjj^  involved  in  the  fj^reat  London  fault. 
There  are  two  strong;  \eins  or  de|)osits  ol  [))rites  carryin^^ 
both  j^old  and  silver,  the  ^anj^ue  ot  one  is  (juart/.  the  other 


calcite.  They  occur  in  the  limestone  in  connection  with  an 
j'nirusive  bed  of  u kite  porphyry.  These  deposits  stand  in  a 
vertical  position,  the  beds  containinjj;-  them  havinji^  been 
turned  up  abvuptl/  against  the  great  London  fault,  by  whose 
movement  the  Archajan  granite  rocks  forming  the  eastern 


_ 


-i.:.4-JW-uMiwwisgiBaiBHiaL_j 


'55 

half  of  Lotuloii  Mt.  .ire  hroujrht  up  into  juxtaposition  witli 
the  Silurian  aiul  (arhoiiik'rous  hrrls  at  its  western  point. 

(ioinj.f  soulii  alon^'  the  .Mos(|Mito  ranj^e  the  intrusive 
j'Oip/iyn'ts  (iiniinish  in  cxtvut  ivtt/  li'it/i  t/triii  iiiso  t/i>-  niiiitrtil 
iicposits. 

The  Sacramento  mine  is  a  j^joorl  example  of  a  "pocket"' 
mine.  Rich  hoflies  of  j^^alcna  and  rich  rjccompost'd  ores 
have  been  found  at  uncertain  intervals  in  a  series  of  p)ckets 
or  cavities.  Some  of  these  poi'kets  or  cavities  an- empty, 
antl    lined    with    mod'.:rn   stalact.lcs,   others  contain    louse 


landonHill 


xt 


Grantt* 


Platk  LXXXV. 

The  London  Mine  Fiult. 

sand,  with  pebbles  of  rich  ore,  others  are  quite  full  of  rich 
ore  deposits.  These  deposits  are  difficult  to  follow  with  any 
decree  of  certainty,  and  much  of  the  profits  made  in  the 
rich  pockets  has  been  used  up  in  blindly  "popherin^"  after 
other  pockets.  From  some  of  these  chambers  open  fissures 
or  jt)int  planes  ascend  \.o  the  surface.  The  limestone  was 
originally  capped  by  a  porphyry  wh.ich  has  since  been 
eroded  off.    7  his  porphyry  doubtless  supplied  the  ore. 

LKADVILI.K    DISTRICT. 

The  western  boundary  of  this  district  is  the  Sawatc'i  ran»;e 
of  Archxan  granite.     The  slope  of  the  Mosquito  rantj  ■  n  t!r 


156 

cast  and  the  hills  on  the  north,  forming  the  water  shed  be- 
tween the  Grand  and  Arkansas  Rivers,  have  a  basis  of 
Archx'an  granite  and  gneiss  more  or  less  covered  bv  patches 
and  remnants  of  the  Paleozoic  formations,  /.  e.,  Cambrian, 
Silurian  and  Carboniferous,  which  have  escaped  erosion. 

Their  lower  position  relative  to  corresponding  beds  on 
the  eastern  or  South  Park  side  of  the  Mosquito  range  is  due 
in  part  to  faulting,  and  in  part  to  folding  of  the  beds. 

Within  these  Paleozoic  f^ormations,  these  beds  of  quartzite 
and  limestone,  ///<7v  is  an  enormous  dc^'clopment  of  erupth'e 
rocks,  principally  quartz-porphyries  partially  occurring  as 
dykes  but  generally  as  immense  intrusive  sheets  following 
the  bedding  plane  of  the  sedimentary  rocks. 

Glaciers  have  been  at  work  also  in  this  neighborho<jd. 
A  huge  "mer  de  glace"  occupied  the  great  valley  of  the 
Arkansas  to  whose  bulk  numerous  side glacierscontr'buted; 
these  glaciers  have  carved  and  sculptured  the  mountains. 
In  the  flood  period  following  the  first  glacial  epoch  a  lake 
was  formed  occupying  the  head  of  the  Arkansas  Valley. 
The  stratified  gravel  and  sand  beds  which  were  deposited 
at  the  bottom  of  this  lake  now  form  terraces  bordering  the 
valley  of  the  .vrkansas  River.  These  beds,  known  as  "wash" 
or  placer  grounds,  yield  gold  and  are  open  to  further 
development.  Lead\  ille  is  the  centei  of  the  mining  district, 
the  ores  are  argentiferous  galena  and  zinc-blende.  They  are 
smelting  ores.  Their  value  is  increased  by  their  having  been 
oxidized,  the  lead  occurring  as  carbonate,  the  silver  as 
chloride  in  a  clayey,  or  else  silicious,  mass  of  hydrated  oxides 
of  iron  and  manganese. 

The  ore  is  principally  confined  to  the  horizon  of  the  "blue" 
or  Lower  Carboniferous  limestone,  covered  by  an  intrusive 
sheet  of  "  white  Leadville  (juartz-porphyry."  The  ore 
bodies  occur  not  only  at  the  immediate  contact  of  these 
rocks,  but  extend  down  in  irregular  pockets  and  chambers 
into  the  mass  of  the  limestone,  sometimes  to  a  depth  of 
loo  feet.  Sometimes  the  ore  completely  replaces  the  lime- 
stone between  two  sheets  of  porphyry,  as  in  the  "Col. 
Sellers  mine,"  Chrysolite,  Little  Pittsburg,  and  on  Fryer 
Hill.  A  few  ore  bodies  occur,  carrying  more  gold  than 
silver,  found  at  other  horizons,  usually  as  "gash"  veins 
running  across  the  stratification  or  along  bedding  jilanes. 
Such  are  the  Colorado  Prince  in  fpiartzite,  the  Tiger  and 
Ontario  in  the  Weber  grits  of  the  Middle  Carboniferous. 

The  "  Printer  Boy."  one  of  the  oldest  mines,  has  pro- 
duced a  good  deal  of  gold,  found  as  free  gold  associated  with 


il- 


ls? 

caiiKJiiate  of  lead  and  ji^alena,  passing  down,  as  is  usual  in 
jj[old  mines,  into  unaltered  auriferous  iron  and  copper  pyrites, 
which  occur  in  a  body  of  (juartz-porphyry  along  a  vertical 
cross-joint  or  fault  plane  in  the  porphyry.  The  gangue  is 
a  white  clay  resultiivj  from  decomposition  of  the  (juartz- 
porphyry  and  though  the  clay  ore  is  rich,  it  shows  no 
minerals  to  the  eye. 

The  Paleozoic  formations,  together  with  the  intrusive 
porphyry  sheets  sandwiched  in  l)etween  them,  have  been 
compressed  into  gentle  folds,  and  where  the  fold  was  at  its 
greatest  tension,  a  series  of  parallel  faults  have  occurred 
having  a  general  north  and  south  directi(^n  ;  their  uplifted 
side  is  generally  to  the  east. 

The  prevailing  eruptive  rock  is  the  "white  Leadville 
|)orphyry,"  occurring  generally  above  the  blue  limestone  but 
also  in  places  below  it  and  at  other  horizons. 

There  are  also  other  intrusive  sheets  of  different  varieties 
of  (juartz-porphyry.  The  ground  is  generally  buried  beneath 
a  hundred  feet  of  glacial  moraine  material,  locally  called 
"  wash." 

The  general  geology  of  the  South  Park  and  Leadville 
region  has  been  so  elaborately  traced  by  the  labors  oi  the 
V.  S.  Geological  Survey  that  we  cannot  do  better  than  give 
an  abstract  of  their  report  in  this  connection  : 

MOSgUITO    RANGK. 

A  study  of  this  range  is  necessary  to  the  understanding 
of  the  Leadville  ore  deposits,  which  occur  on  its  western 
side.  It  comprises  a  length  of  19  miles  along  the  crest  of 
the  range,  and  in  width  including  its  foothills  bordering  the 
Arkansas  Valley  on  the  west,  and  South  I^ark  on  the  east, 
a  slope,  in  one  case  of  7^  miles,  and  in  the  other  of  about  9 
miles.     All  of  it  is  about  10,000  feet  above  the  sea  level. 

The  range  has  a  sharp  single  crest  trending  north  and 
south.  To  the  west  this  crest  presents  abrupt  cliffs  de- 
scending precipitously  into  great  glacial  amphitheatres  at 
the  head  of  the  streams  flowing  from  the  range.  Mts. 
Bross,  Cameron  and  Lincoln  constitute  an  independent 
uplift.  The  abrupt  slope  west  of  the  crest  is  due  to  a  great 
fault  extending  along  its  foot,  by  which  the  western  con- 
tinuation of  the  sedimentary  beds,  which  sNjpe  up  the  east- 
ern spurs  and  cap  the  crest,  are  found  at  a  very  much  lower 
elevation  on  the  western  spurs.  The  jagged  step-like  out- 
line of  the  western  spurs  is  due  to  a  series  of  minor  paral- 
lel faults  and  folds. 


^i 


iiii 


158 

The  secondary  uplift  of  Sheep  Mountain  on  the  eastern 
slope  is  due  to  a  second  f^reat  ioU\  and  fault. 

'I  he  elevation  of  Mount  Lincoln  is  the  result  of  the  coni- 
hination  of  forces  which  have  uplifted  the  Mosquito  ranj^e 
and  those  which  built  up  the  transverse  ridge  separatinj^ 
the  Middle  from  the  South  Park. 

The  range  has  been  sculptured  bj-  glaciers  into  canyons, 
and  the  ArU.iMSci«;  valley  is  covered  with  horizontal  terraces 
representing  the  crstribution  of  material  by  waters,  <jn  the 
melting  of  the  glaciers. 

In  the  seas  of  thv"  Paleozoic  and  Mesozoic  eras  which 
surrounded  the  Sawatnh  islands,  some  10,000  to  12,000  feet 
of  sandstones,  conglomerates,  doloniitic  limestones  and 
shales  were  deposited.  Towards  the  close  of  the  Cretaceous, 
eruptions  occurred  by  which  enormous  masses  of  erupt- 
ive rock  were  intruded  through  the  Archaean  floor  into  the 
overlying  sedimentary  beds,  cnjssing  some  01  the  beds,  and 
then  spreading  out  in  immense  intrusive  sheets  along  the 
planes  of  division  between  the  different  strata. 

The  intrusive  ftjrce  must  have  been  very  great,  since  com- 
paratively thin  sheets  of  molten  rock  were  forced  continu- 
ously for  distances  of  many  miles  between  the  sedimentar\' 
beds. 

That  the  eruptions  were  intermittent  and  continued  for  a 
long  time  is  shown  by  the  great  variety  of  eruptive  rocks 
found.  That  this  eruptive  activity  preceded  the  great  mo\e- 
ment  at  the  close  of  the  Cretaceous,  which  uplifted  the 
Mosquito  range  as  well  as  Jie  other  Rocky  Mountain  ranges, 
is  proved  by  the  folding  and  faulting  of  the  porphyry  erup- 
tions themselves. 

In  the  period  intervening  between  the  cKjse  of  the  Cre- 
taceous and  the  depijsition  of  the  Tertiary  strata,  during 
which  the  waters  ot^  the  ocean  gradually  receded  from  the 
Rocky  Mountain  region,  the  pent-up  forces  of  contraction 
in  the  earth's  crust,  which  had  been  long  accumulating, 
found  expression  in  dynamic  movements  of  the  rocky  strata, 
pushing  together  from  the  east  and  the  west  the  more  re- 
cent stratified  rocks  against  the  relatively  rigid  masses  of 
the  Arcluean  land,  and  thus  folding  and  crumpling  the  beds 
in  the  vicinitv  of  the  shore  lines. 

The  crystalline  and  already  contorted  beds  of  the  Archa'ai> 
doubtless  received  fresh  crumples  in  this  movement. 

A  minor  force  also  acted  north  and  south,  producing 
gentle  lateial  folds  along  the  foothills  at  right  angles  to  the 
trend  of  the  range.    These  intjvements  were  not  paroxysmal 


II 


^lllu^^t^^>uc^  aiiu  anai^^o    vwiii| 


/v/ui  lie 


neii?hbi)rho()d.    which    are  le^s  susceptible  to  percolatinjr 
-      ~  •  ■    formations  in  America  arc  the   prin- 


w 


ater.     The  Paleozoic 


ripal  repositories 


for  lead  and  silver  ores,  not  by  reason   ol 


their  j^^eological  age,  so  much  as  by  their  containinfi:  such  a 
[uantity  of  soluble    limestones  and  being  physically  as  wel 


»59 

or  siiflrleii  and  x'iolciit,  but  [n'otnictcd  for  an  cnornious  lapse 
of  time,  and  apjicar  to  be  continued  in  diniinisbed  force  up 
to  the  present  day. 


J^li  ro  Tr-i  us 
Car 
SUu 


C'reKctceni  t, 
itJufct  'I  r  I  c/J 


ojf  oiciScct- 


Crvi'^it  r  an  .•>  — . 
iMfa  /'ri'txa  ■ 
Cay  ton  iftrau 


^SIxufettcH  Myvfiaaanys^omU 


^Si!=^:- 


o- 


litc  rteof 


\.'.  /.      /•/,•(!/  Sntii'H,  x/ii>;.'iii,i^  I'tt/ro'^i'.U  a  ml  Mcsozoic  Strata,  i''ith  inn  us  ions  of  eruptive  KocK\  Iviiti;  hinealh 

Mouiiiiiiii  etrvation  at  I'iose  o/'  (  ret  a 
\-    Crttaceous  --^ 
3   t/ixrci  Trices    -, 
t~  Carbont/67x>tia     , 
GrctntC*.. y   {/    I    \^^j^iti^Tia*:  ^        )  \,^M^»oxoia^  /mS*j5--  /r 


•>,.■>..,       ,  ,       , 


>Af.O'3Vuifr>  /i^trliyf 


Ct'OKl 


.Vo.  a.      /</ea/Se,tio»,.W,o:rif>,;  yes;i.'{  ,./(/,,  j^i.-.tt  IVt  (  'et.ueous  ii/>/i/t 


cXu^a^c'^i  /iuriff 


Xfciifu r.'o  fill  ngrr 

.\r.  3.     A7fr,if:'  Seition  0/  Lra,Hii/e  Distri,  t,  Mos./uilo  A'amr  aii.i  South  l'a>  -;■  as  it  is 

I'l.ATI.  I.XXXVl. 
Sections  to  IlliiNtnitc  the  ('.railti.-il  CKoL.nii  •«!  I  tcvclopmeiu  <>i  ilw  I..-, 


neij^hborhood,  wliich  are  less  susceptible  to  percolating,' 
water.  The  Paleo/oic  formations  in  America  are  the  prin- 
cipal repositories  for  lead  and  silver  ores,  not  bv  reason  of 
their  ^eolopical  aj,>^e.  so  much  as  by  their  containinp^  such  a 
quantity  of  soluble    limestones  and  being  physically  as  well 


Diis  lapse 
force  up 


/Sta 


Carton  i/rrtji4a_      \ 


tTn  rctTricta 

Ca  rb  o  n  lye,  r-ou»i\ 


Cffnrx  t'Jtc  Fteof 


CSolorciolv Fi~ont  I^anjyo  latarxdt 


IS  of  ffupiive  RiHk\  lyiiiK  h>  neatlt  thi'  Mesozoic  Sea,  bitween  Sawatch  and  Front  Kan,i,t  /s/aiuh  prior  to  the  great 
tiiii  in  cli-'ittion  iit  i  lost-  <\/'  (  ri'/in  tons. 

CretaccoLca 
>7icrct7~i~ia.a 


C^otrtZH  J^'ctf/c  Jja-sin. 


Color'acla /■'ron.t  flancyu  t//oli/t 


'' '/,,  f,  I  III'  ro.it  I  '■rtaiioiix  Hpii/t  and  the  folding  up  of  the  Mosquito  Range. 


batHa 


^cii"'  ncff  PO'Sifi 


Cotoraeit  /T-vytt^anffV 


McifuHf  fia  rigr* 

'(>  A'ani;r  and  Sou//i  /'a>  i-  as  it  is  today,  shoiving  result  of  faulting  and  subsequent  erosion. 

PlatkLXXXVI. 

leological  DcvelojimciU  nf  ilie  I.cadvillc  and  SoiUli  Park  Region,  Colorado. 


percolatinjj; 
I  the  prin- 
■  reason  ol 
iiiiip  sucli  a 
:ally  as  well 


m 


T58 

Tlie  secondary  uplift  of  Slieeji   Mouiif.\in  on  the  ca*  tern 
slope  is  due  to  a  second  p^reat  fold  and  '".tult. 
-  'I  he  elevation  of  Mount  Lincoln  is  the  result  of  the  coin- 


li) 


m  1 


7}H 


I 


in  the  vicinitv  of  the  shore  lines. 

The  crystafline  and  already  contorted  hedsof  the  Archa-an 
doubtless  received  fresh  crumples  in  this  movement. 

A  tninor  force  also  acted  north  and  south,  producinji^ 
fifentle  lateral  folds  alon^  the  fo(jthills  at  ri^ht  angles  to  the 
trend  of  the  range.     These  movements  were  not  paroxysmal 


•59 

or  siidflcii  and  \-i()lent,  but  protracted  for  an  enormous  lapse 
of  time,  and  appear  to  be  ccjutinued  in  diminislicd  force  up 
to  the  present  day. 

MINF.KAI,     DKPOSITIDN. 

It  was  during  the  period   intcrveniufj^  between  th(.'   intru- 
sion of  the  eruptive    rocks   and   the   dynamic    UKnements 


which  uphfted  the  Moscpiito  range,  that  the  original  leposi- 
tions  of  metallic  minerals  occurred  in  the  Learhille  region 
in  the  form  of  metallic  sulphides,  though  now  thevare  fouiul 
largely  oxidized  and  in  other  combinations.  The\-  were 
derived  from  the  eruptixe  rocks  themselves  un(]  are  there- 
fore of  later  formation  than  they.  Their  having  been  folded 
and  faulted  with  them  shows  that  they  must  !ia\e  been 
formed  before  the  great  Cretaceou'  uplift,  and  therefore 
they  are  Ider  than  the  Moscjuito  ra  •  ,  itself.  The  depo:::iL.i 
we-  _•  formed  by  the  action  of  perc(jla'ing  waters  taking  up 
certain  ore  materials  in  their  passage  hrough  neigliboring 
rocks,  and  depositing  them  in  more  c(  ircntrated  form  in 
their  present  position.  This  may  ha\  e  taken  place  while 
the  sedimentary  beds  were  still  coxered  by  the  waters  of 
the  ocean,  and  the  waters  therefore  may  have  been  derived 
from  it.  or  the  area  of  the  Mos(piito  range  may  have  already 
emerged  from  the  ocean  and  the  wa.ters  ha\e  been  estuarine. 
The  uplift  of  the  Mos(piito  range  consisted  of  a  series  of 
folds  fractured  by  faults.  The  crest  is  formed  by  the 
.Mos(piito  fault,  auf^ther  parallel  fracture  is  the  London 
fault.     Tl 


_   greatest  movement    is   towards   the   center   or 

Leadville  region,  dying  out  at  either  end  north  and  south  ; 
the  greatest  displacement  is  lo.ooo  feet.  Whatever  cliffs 
may  ha\e  (originally  been  formed  by  this  faulting  hax'C  been 
planed  down  b\'  glacial  erosion. 

ORIGIN'    OF    r.EADVIM.K   ORK    DF-'.I'O.SITS. 

The  ores  are  deposited  for  the  most  part  in  the  blue  lime- 
stone of  the  Lower  Carboniferous.  As  the  ores  were  de- 
posited by  water  solutions,  the  soluble  limestone  beds 
would  be  more  easily  acted  upon  by  solutions  than  the 
sandstones  and  shales  composing  the  other  locks  of  the 
neighborhood,  which  are  less  susceptible  to  percolating 
water.  The  Paleozoic  formations  in  America  are  the  j)rin- 
cipal  repositories  for  lead  and  silver  ores,  not  by  reason  of 
their  geological  age,  so  much  as  by  their  containing  such  a 
quantity  of  soluble   limestones  and  being  physically  as  well 


aagj 


i6o 


as  chemically  favorable  for  the   reception    of  mineral    solu- 
tions. 

'I'Ik-  physical  structural  conditions  of  Leadville  are  par- 
ticularly favorable  to  the  concentration  of  percolating^ 
waters  in  the  blue  limestone,  (ireat  intrusive  sheets  of 
porphyry  follow  the  limestone  persistently,  principally  on 
its  upper  surface.  'I'his  porphyry  is  very  porous,  and  full  of 
cracks  and  joints,  alTordin^  reafly  channids  for  water  from 
above,  and  also  channels  for  ascenrlin^  water  from  below, 
al«)nfi^  the  walls  of  the  fissures,  through  which  it  is  irrupted. 
Such  waters  passing  tin  ou)j^h  a  medium  ol  dilTerent  compo- 
sition would  be  reafly  for  a  chemical  interchange  with  the 
limestone. 

COMI'OSI  rioN    Ol'    OKKS. 

The  ores  were  flenositcfl  originally  as  sulphides,  'i'his  is 
shown  by  the  fact  tliat  the  oxidi/c'd  ores  near  the  surface 
()ass  down  with  depth  into  sulphifles.  In  Tfn-.Mile  district 
these  oxidi/ed  ores  are  seen  to  result  from  tUr  alteration  of 
a  mixture  of  galena,  pyrite,  and  zinc-blenfle.  There  is  very 
little  gold  in  tlu;av»'rage  Leadville  ort.'s  ;  what  little  there  is 
comes  from  the  Morence  niine  (native  gold),  anrl  from 
others  where  it  is  associated  with  pyrites.  It  is  usually  as- 
sociated with  porphyry  rocks,  and  a  porphyry  commonly 
called  pyritiferous  porphyry  shows  gold  to  exist  dillusefi 
through  the  pyrites  disseminated  through  its  mass. 

Si'k'er  occurs  aschlorifie,  a  seconrlary  condition,  its  orig- 
inal condition  probably  being  sulphide. 

Z,^rtr/ occurs  as  carbonate  anfl  sulphate  and,  deeji  in  the 
mines,  as  sulphide.  Specim(;ns  are  common  of  galena  noflules 
surrounded  by  a  thin  coat  of  sulphatt!,  and  that  again  by  a 
coat  of  carbonate,  showing  the  order  of  transition  from  sul- 
I)hide  to  sulphate  and  thence  to  carbonate. 

In  the  iron  mine  native  sulphur  occurs  as  an  alteration 
product  of  galena. 

Iron  ■.\\\i\  tnniti^dfiesi'  covx^iMwU"  rather  a  ganguc  material 
th.an  an  ore.  'I  liey  are  hydrated  oxides  and  protoxides.  The 
iron  was  originally  deposited  as  sulphide  or  p/yrites,  but  has 
been  wholly  transformi'd  by  oxidation. 

/.in(  is  not  common,  but  occurs  as  calamine  (zinc  silicate) 
in  needle-like  hairs  and  white  crystals  in  cavities  in  the 
mines.  Its  original  form  was  zinc-blende  (zinc  sulphide),  as 
shown  in  the  Ten-Mile  district. 

The  earthy  minerals,  alumina,  lime,  silica  and  magnesia, 
are  in  fair  proportions,  as  might  be  ex|)ected  from  ores 
which  are  a  re|)lacement  of    limestone   in   cU^sc   connection 


ft^ifi  ^ 


.«WHMW*<MIiV|lS'^«^ 


\(>\ 


olu- 

):ir- 

<>i 
"II 

I  of 

Olll 

i*\V, 

Irrl. 

)')- 

lit- 


witli  pin  |)li\  TV.   'Ill*'  ;ill\:iliiic  cIciiuMit  iiinoiij^  the  ores  mij^'lit 
also  hf  t  ia(  (.'(i  (o  tlu-  IiiIIul'iicc  of  tlie  latter  rock. 

The  aj^n'iits  of  alt(.'ratioii  were  surface.' waters,  which  con- 
tain evervwhcrc  carhoiiic  acirl,  o.wfj^en,  orj^anic  matter, 
chlorifle  of  sodium  (common  salt ).  an(l  |)hos|)horic  acid.  The 
rocks  through  which  these  wat(;rs  passefl,  such  as  |)or- 
nhyries  and  limestones,  were  found  to  contain  phosphoric 
cid  and  chlorine,  whih;  <»rjjjanic  matter  exists  in  the  hliie 
■  mestones  ;  and  in  the  ov(;rlyinj.f  shales  and  sandstones  arc 
'uany  carhonaccous  l)«;ds  and  even  heds  of  coril.  Water 
passing  throu;.(h  these  rocks  would  take  up  all  these  tde- 
menls  and  he  nafly  for  chemical  reactions. 

f/(?A7/<Mlead  Md|)hide)  is  much  richer  in  silver  than  its 
alteration  produ(  t,  carhonate  of  lead,  or  cerussite.  ( )ii  ("ar- 
honatt:  Mill  the  carhonate  averaj.^es  40  o/.  siKcr,  the  j^alena 
is  145  o/.  to  the  ton.     Hut  {.galena  is  harder  of  treatment. 

SilvM-r  is  found  at  times  disseminated  throiif;;h  vein  matter 
and  countrv  rock,  without  the  j)resence  of  lead,  proxinj.; 
that  dtirinjj;  alteration  siKer  was  removed  farther  liom  its 
oriv^inal  condition  and  n\or(,'  wid(dy  disseminated   than    lead. 

( )utcr(j|)  de|)osits  have  proved  in  n  ny  cases  richei  thaiv 
those  at  depth.  The  fleposits  near  the  surface  have  hei-n 
the  refined,  concentrated  remains  of  lar^^tM'  hoflies  j.,nadually 
remo\ed  hv  erosion,  as  the  altt.-ration  hy  surface  waters  went 
on.  'I  he  haser  and  more  soluhle  metals  have  thus  heen  re- 
moved in  solutions,  lea\injj^  hehind  the  more  valuahle  and 
perha|)s  less  soluhle  metals  in  new  and  richer  se(  oudary 
cond)inations. 

"  Knoliii"  or  "Chinese  talc,"  which  occurs  !.>oth  alouj^^the 
line  of  contact  and  hetween  tlu;  porphyry  and  limestone 
and  also  in  the  heart  of  the  ore  depcjsit,  is  a  decomposition 
[Modiict  frf)m  porphvry.  It  consists  principally  of  hydrated 
silicate  of  altniiina  derivefl  trom  tlu;  feldspars  (d  the  p(n'- 
phyries,  perhaps  at  the  time  when  acted  upon  hy  sulphurous, 
waters,  which  hrouj^dit  in  the  orijj;inal  oie  deposits. 

t ■<//(//<•  occurs  incruslin^  lecent  cre\'ices  aiul  linin>.j  iccent 
cax'ities. 

luvitc  is  Common,  j.(enerally  associated  with  chloride  of 
siK'er  aufl  manj.ranese  and  is  lorally  rcco}inizi\{  as  a  si)^n  of 
rich  ore. 


\lnl)l.   ()!•    |(»U\I  \  I  ION    01     l,i:.\l)\II.I,K   (tKI.    l>KI'osrr>>. 

'I'heores  were  depositerl  from  water  solutions  h\' a  metaso- 
niatic  interchaiif^'^e.  /.  <■..  suhstance  e.xchanjj^efl  for  sul)staiu:tr 
with  the  linu-  'oiu-  ;  aiul  lastly  <  .•  orij^inally  as  sulphides. 


1' 


— •      % 


!  r 


Miiu'ial  iniilfcr  is  caniffl  fmin  i  ,H'  phx'c  jn  aiiothci  w  itiiin 
the  earth's  crust  l)\-  liraf  anrl  wattT.  <>r  tlu-sr  cumhiiu-d. 
MiiasDinatic  iiitcrc  liaiijj^c  <»l  imtal  tor  limi'stoiu"  and  tlic 
rem<)\-al  of  (loloiniff  could  only  lia\  c  l)»'rn  prorlnccd  i)y 
water.  'I'lu.' oil's  wcic  ;/(>/  deposited  in  />ri-i'v/sf/Hi^  iin'///is, 
but  are  a  replacement  of  the  k'onntry  rock.  /.  <-.,  doloinitic 
hinestone. 

The  ores  ^M.ide  oil  j^Madnall)  into  !  he  material  ol  tlie  linn- 
stone,  with  a  delinile  limit,  as  would  n<tl  ha\'e  been  the  case 
it  the  limestone  had  heen  pr"\iousIy  ca\ crned.  'I'he  onl\' 
limitinf.j  outline  to  the  ore  bodies  is  that  formed  b\  the  ion- 
tact  porphxry. 

I''raj4;nu'nts  <i|  unalteicd  limestone  are  found  entirely 
encl'ised  within  the  ore  bodies,  and  ore  bodies  often  occupy 
the  entire  space  for  lonj^  distances  between  two  horizontal 
sheets  of  porphyrs,  which  s|)ace  further  on  is  occu|)ied  by 
the  limestom,'.  This  is  well  seen  in  Colonel  Sellers  mine. 
Kxamination  of  ores  and  \einstone  shows  linte  and  nia^'ne- 
si.i  not  in  the  crystalline  condition  they  would  have,  had 
thev  bt'cn  bronjLrhi  into  a  pre-exist  inj^^  cavity  and  deposited, 
but  in  the  same  jj;r.inidar  i  ondition  in  which  tlu-y  exist  in  the 
Country  rock. 

'I"he  deposits  in  rocks  oflu-r  than  limotone  consist  of 
met.illic  miner.ds  and  of  alfereri  portions  ol  ihe  conntiy 
rock,  in  whicli  the  structure  of  the  latter  can  sometimes 
be  still  traced,  and  are  not  tlu"  reirular  layers  of  mattei 
forti.i,Mi  to  the  Country  rock,  which  results  iiom  the  lillint: 
<it  a  pre-existin/j;  tissure  or  cavity  by  materials  l)rouj.,dit  in 
from  a  rlistance  and  tleposiit-d  alonjjf  the  walls. 

In  the  Ten-Mile  disl  lict  the  arrangement  ol  the  particles 
<)t  the  orij^ina!  rock  is  frcMpienliy  seen  lobe  |)reser\ed  in 
the  mi'tallic  minerals,  which  maintain  a  certain  parallelism 
vith  the  original  beddiiij,^  plaius  in  the  lines  defined  by 
iniiuite  chanjj^es  in  these  minerals. 

Tlu'  common  characteristic  of  ca\'es  whi<h  have  been  dis- 
solved out  of  limestone  is.  that  their  walls  are  coated  wil  h 
;i  layer  of  clay  which  has  been  left  inidissoKed  by  the  per- 
colating' waters,  and  these  walls  have  ;i  peculiar  surlace  of 
little  cup-shapi'd  irn'f^ularities  from  which  also  stalactites 
fre([uently  hanj,;.  There  is  also  an  accumulation  at  the  l<ot- 
tom  of  the  cave  of  fiajj[ments  of  limestone,  fallen  from  the 
sides  of  the  roof.  None  of  these  characteristics  are  fouiul 
associated  with  the  ore  replacements. 

Also,  when  mineral  matter  is  deposited  in  "  pre-exist  in;,,' 
cavities"   it    takes    the   form  of   ri'f^'ular  layers  parallel  with 


">3 

tlic  walls  of  the  cavity,  as  is  hi-autitiilly  slmwii  in  >4:fuflcs 
liiu'd  with  a  sm  •.-cssion  ol  /i-ulitcs  m  with  hiMisot  clial- 
Cfdoiiy.  <»[)al  and  (|uait/. 

No  siicli  sucti'ssivo  arranjjfLMront  in  layers  is  toijiul  in  the 
I.cadxilk.'  ore  bodies. 

A^Min.  (-onid  such  laijj^i-,  open  cavities  have  existid  lor 
\<>u^  distances  without  support  between  the  layers  ot  por- 
phyiN?  Why  did  not  tlu'se  porphyry  sheets  close  tojj^ether? 
Aiifl  lurther,  howcould  such  extensixc  ca\ilies  liaMheen 
formed  and  ki-pl  open  undi.-r  a  pressure  of  lo.ooo  feet  of 
rock,  which  the  jj;eo|oj^y  of  tlu'  rejjfion  shows  to  lia\i' existed 
aho\"e  the  fleposits  at  the  time  tliey  were  heinj^j  formed? 
Such  ca\ities  as  we  do  I'md  in  the  n-jj^ion  are  all  ol  \ery 
recent  orijj;in.  cutting;  throuy^h  both  limestone  ai\d  ore  bodies, 
and  ha\e  been  bollowi-d  out  by  surl.ic*-  w. iters  more  lecent 
e\'en  than  those  which  produced  the  secondary  alter. itions 
in  the  ore  bodies. 

'Ihe  ore  deposits  of  'l"en-Mile  district  .d)ont  Kokoiuo,  not 
far  north  from  Lead\  ilk-,  are  \ery  similar  in  chara(  ter  to 
those  at  Leadxille.  Thev  occur,  however,  in  a  somewhat 
hij^her  di\ision  of  the  (  arboniferous,  .ind  the  ores  as  a  rule 
are  not  so  decomnosed  and  o.\idi/e:l,  and  the  transiti(»n  from 
the  orijj^inal  sulpliifle  character  of  fhe  deposits  totheo.xi- 
di/efl  Condition  is  more  easily  shown. 


Ki:i)   (  l,ll-|     «;n|  I)    Kl.l'nsilS. 


At  Rv(]  riitf,  still  further  north  of  I.eadville.  in  the  N'alley 
of  the  Kaj.jle.  the  s.inu'  j^eoloj^ic"  s  .ries  are  lound.  penetrated, 
as  at  I.eadville  anrl  Kokoino.  by  eruptive  sheets.  In  the 
limestones  at  contact  with  the  porph\  ries,  much  the  >iime 
classes  of  ore  depi<sits  occur,  but  the  peculiar  and  instruct- 
ive feature  of  the  camp  is  Ihe  rich  deposits  of  j^'olfl  in 
chand)ers  and  cavities  in  the  harri  and  usually  un])iofiii(t  i\e 
('and)rian  (uiart/ites  restinj.^  on  the  granite. 

The  ^n\(\  in  these  chambers  often  occurs  as  nuj,f;fets.. 
'Ihe  ipiaitzites  rlip  about  lo  \.  K..  aiul  between  their  befi- 
dinj^  planes  lies  tlie  ou.  'I'lie  so-called  contact  or  beddintj 
plane  betwi'en  one  stratum  of  (piartzite  anrl  another  is 
clearly  det'iufd  At  this  line  there  is  a  tilling  so  to  speak 
of  "  brecciated.  broken  up  (piartzite  frajj^ments  cemented 
by  iron  rust  and  at  times  i)y  iron  pyrites.  The  thickiuss  ot 
this  breccia  varies  between  four  and  six  feet.  Ore  cliim- 
nevs  on  this  breccia  occur  at  interxals. 


ir.4 


Their  prt'scnrc  is  iiwlicatfrl  on  tlu-  niitcnip  bv  scinis  of 
nist\  clay,  which  hcs  on  t<t|)  ol  Ihc  «»rc  hody  iiiid  lullows  it 
;iI<iiijj:  thi;  root  of  the  dt'p./sit  tor  loo  to  200  Icct,  then  thins 
■ont  j^Tii(Ui;iII\-  and  disappears  entirely;  at  the  point  ol  's 
<lisappearance,  unaltered  Iron  nyrites  set  in. 

These  «)ro  chimneys  ar»!  ahoni  4  teet  in  width,  their  thick- 
ness i;,  limited  to  the  space  between  the  Ijoor  ;infl  I'ool. 
The  (piart/ite  root  is  always  snioolh,  but  the  lower  (piart/- 
ite  lloor  is  nuij^h  and  corrnj^ated  and  shows  chemical  action 
on  it  attendant  on  deposition  ot  ore.  The  floor  at  times  is 
impre^oialed  with  ore  which  does  not.  howeser.  extend  any 
jj^reat  distance  into  it.  Thouy:h  the  ore  chimneys  are  from 
4  to  T)  fret  wide  the  pay  ore  is  only  a  few  inches,  swellini; 
from  floor  to  roof.  '1  he  pay  ore  in  the  o.Nidi/ed  iust\'  por- 
tion yields  7  ounces  ^nU]  anrl  50  ounces  silver. 

In  minini.;;.  the  floor  is  followed  as  a  jj^nide.  Indi\idual  ore 
<.iiimne\s  are  connected  laterally  by  ore  chutes  like  a 
network.  These  ore  chimneys  divide  and  separate,  the 
branches  ri'unitinj.,'  or  ajj^ain  s|)litt inj.;  un.  The  whole  rami- 
fication comes  together  a^.iin  at  intervals  in  one  main  chim- 
ney. The  rock  filling-  the  space  where  the  di\erjj;'ence  has 
taken  place  is  the  same  as  the  i)reccia  tilling,  onl\'  more 
Compact  and  imprejj^nated  with  pyrite.  These  tillinj.|[s  are 
left  staiulinjj;  as  pillars  after  the  ore  is  mined. 

To  sum  up.  the  characteristics  of  tlu-se  de|)osits  are  ; 

I'irst.  I  he  outcrop  of  the  ore  chimney  indicated  1)\  what 
is  locally  called  a  "joint-clay." 

Siconii,  A '/one  of  oxidation  for  2'X)  feet,  which  j.'^iadually 
iiierj^es.  as  the  natural  wati-r  le\'el  's  approached,  throuj^di  a 
y^one  of  mi.\ed  o.xides  and  sulphiffi's  to  'he  zone  ol  unal- 
fected  sulphides. 

T/iird.  The  "joint-clay  "  gradually  disappears  as  the  sul- 
phides are  appnached.  The  ore  on  analysis  shows  sescpii- 
.oxide  and  sesipnsulphate  of  iron,  silica  anrl  alumina  and  sul- 
phate of  barium. 

lutheGrouiifl  lio^  mine  the  ore  chimneys  are  600  fei't 
apart  but  are  probai)ly  connected.  They  abouufl  in  nuj.^- 
gets ;  the  latter  are  sometimes  twisted  like  bent  horns;  in 
other  chutes  they  are  lumpv.  composed  of  crystalline  jj[old 
particles  cen^^ented  together  b\-  sestpiisulphate  of  iron  and 
liorn  silver. 

Nuggets  are  found  in  troughs  in  the  (piart/ite  floor  im- 
bedded in  clay  associated  with  rich  siKer  or  horn  silver 
ore.  With  the  nuggets  are  lumjis  of  sescpiisulphate  of  iron 
<'arryiug  much  gold.     This  proves,  according  to  .Mr.  (iuiter- 


inuM.  tlKit  tin-  st'('iinf1;iiy  flcpMsit inn  ni  jr<ilM  in  crV'it.ils  \v;i« 
tlii<)iif.fh  tin-  iiK'flimn  nt  prisulpliatc  o|  inni  rli-ru-i'd  hum 
slow  oxidation  ot  iron  pyiitrs,  and  is  an  adinirahlc  (  nniit- 
njation  <»|  the  theory  .is  statrd  hy  I'mt.  I.i-  C">ntc  in  his 
(icology. 


ASl'IN    OKI     |)|  I'o^l  I  s. 


I'hf  AsptM   niininj^'  ri'j^ioii  is  jj^eolofj^icaljy  trlai"<i  to  lli.it 


la-an 


of  I.cafhilif  ;  each  is  uii  thf  shore  Min-   i>l   i\\r  old 

island  ot   ihf  Sawalch.  oiii'  on    tlu-   cast,   tin-  other  on  ilic 

west,  opposite  one  another,  hnt  ahont  50  miles  apart. 

The  ore  di'posits  occur  in  the  same  general  hori/on.  vi/., 
t  he  Lower  (arhoniteroiis. 

Both  rej^fions  show  intensi-  disturbance,  both  l)\'  N'olcanic 
intrusions  o|  igneous  rock.  loldiiij.r,  and  tanltin^.  The  pro- 
i'ess  ol  ore  di'position  in  hoth  rej.(ions  has  heen  ii;i  actual 
replacement  of  the  country  rock  hy  \'ein  material. 

At  Aspen  the  ore  is  not  found  in  lUtuiil  contac  t  with  the 
o\erl\  iny:  erupti\e  ij.rneous  rock,  hut  at  some  d-pth  down  in 
the  limestone,  at  a  zoiu'  where  the  "  blue  limi's<one  '  be- 
comes dolomi/ed.  or  as  Aspen  miners  say  "passes  from 
blu'-  lime  into  short  lime." 

The  mines  ol  Aspen  are  situati'd  in  I'aleo/oic  strata 
reclininj.,'-  upon  the  slope  of  a  narrow  rid^M-d  mountain, 
forminj^'  a  j.franite  spur  "  rii  tr/ir/ou  "  with  the  Sawalch  ranj^e. 

The  strip  of  Count  ry  in  the  \icinity  of  Aspen  constitutes 
the  di\idinf;  line  between  the  t\>'o  distinct  uplifts  of  the 
Sawatch  ranj^e  on  Ihei-ast.and  the  l'!lk  mountains  on  the 
west,  and  has  been    successivelx'  atlected    by  i-ai  h  uphea\al. 

The  Sawatch  uphea\al  was  a  ).fradual  elevation  of  this 
mountain  mass  ri-sultinjj:  from  a  j.jradual  suhndence  of  the 
adjoininj.f  sea  bottoms,  which  taused  t he  sediicicntary  beds 
deposited  in  those  sea  bottoms  to  slope  up  at  N'aryin^: 
anjj^Ies  all  alonji^  tin*  ancii-nt  shore  line  toward  the  central 
m:\-s  of  the  Archa-an  isl.ind. 

Tiie  KIk  Mountain  ranj^a'.  which  extends  to  the  west  and 
south  of  t'"s  rejj^ion.  was  u|)hea\'.'d  lati'r  than  th.e  Sawatcli. 
wilhf^reatn  \io|ence  an(Uru|)ti\e  enerjj^v.  and  the  uplua\al 
was  accoi)))  inied  by  cikhmuous  intrusions  of  erupti\'e  rock 
uhi'h  wtre  forced  into  the  sediinentarv  strata  alreadv 
shattered  by  the  lorces  of  upheaxal.  in  j.^H'at  "  lac( olites."  or 
solid  masses,  and  spread  out  throu>j;h  them  in  e\ery 
direction   in  the  form  of  d\kes  and    intrusive   sheets.     The 

)1 
w 


surface  exposures  of  thesi-  i^^neous  bodies  co\'er  areas  < 
twenty-five  to  thirty  scjuare  miles,  and  their  extension  belo 
the  surface  is  doubtless  very  much  f,freater. 


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I  III'    mil  IIM<  >ll    I  •!    MK   ll    I    III  II  11)1  i|lN 

masses  III  iMiri^n  iiMltn  niiist  ii<>l 
olilv  li.i\r  ^H'.ilK  (Ii^IiiiIhiI  ihi 
ImwIs     williiii     iIh'     I  (7411111    III     II  |i 

lir.lV.ll.  lilll    .iImi   Ii,I\<     S.I  I    \|i,ll|(lr(| 

I  III-  \  I  >lnmf  I  il  I  ln'  1,11 1  h  s  (  I  list  III 
this  .inM  ;is  III  I  Miisi  .1  s('\(ii 
l.ilri.il  |iii'ssiiii  III  ilir  .III ji lining 
ir^imi.  Tli.il  .iil|i  1111111)4  irL',iiiii 
W.is  ,\s|Hii  .mil  Its  iiriLjliln  i|  III  i<  xl, 
h  u  I  mill  III'  |iis|  ill  I  III'  s|  I  i|i  III 
srijiiiii  iil.ii  \  Inil'.  .1I111114  till'  ,\s|>rn 
Mniiiil.im  111I141'.  wliii  ll  Is  li.ii  Kill 
li\  ,1  |iii  iji'i  I  III);  |>iiml  III  llir  nil 
\  irldlll);  S.IW  ill  ll  .\li  li.r.ill.  1  ll.il 
lliis  11  iiii|iii'ssii  111    wnnM    !tr    iimsl 

sr\  r|il\  li'll,  I  lir  S.iw.llill  j.',l.llil|i' 
lll.iss  .11  1 1 1114  .IS  .1  I II  lilll  III  irsisl.iiK  (• 
.Ij^.lllisl  llir  mlriisr  l.ll  r  1 .1 1  i  1  HII  |  il  fs- 
s|iili  I  .iiisi'il  li\  llir  \iiim^ri  I'lk 
M-.iml.im  ii|ilill.  i^    :;^ 

llir     SI  liiiiiriil.ii  \      lulls      |rs||||)4  ""  !_^ 

il^.ljlisl     111!      AicliiiMii    (  III  irs|iitM»l  f^  ^ 

)^riiri,ill\  .    uitli    slit;lil    ilillrirncrs.  5  X 

In  lliiisi'   III   I  111     s,, lilll    iViiK    .mil  ii  X 

l.r.liU  llli'    li'l^liill    111   ,1     silllll.ll    |iitsi  I       < 

limi.  ^    tZ 

llir  l.illi  I  will'  ilr|>i  islli  ll  ill  .1  P  •""" 
|MI  I  i.lll\  I  III  ll  isril  l»,i\  .  Ill  i\\  1  I  iiis|  I 
I  III  111)4  I  III  Si  >I||  ll  I  '.II  k  ll.lSlll.  I  111' 
liilliH'l  iiii  llir  Wisl  sulr  m|  llir 
,\ii  ii.r.iii  isl.md  III  ,1  null  1  ,mil 
«|rr|(ri  sr.i.  iiliil  oil  lliis  ursli  111 
s|ii|ir  llif  Im'iIs  ,iu'  j^riHi.illx  nun  li 
lilll  kri  I  li.m  I  hose  ul   i  i  n  irs|ii  mil 

inK  K''"'"^"  ■•'  li"ii/i"i'  I'll  IIk' 
<'nst. 

Ml'  \  Mi.lMI'll\    III       \s|'l  \. 
I .     llir   III  i|  l/i  HIS  |i'|iirsi'|||i'i|   .lie 

1  In-  I  |»|iii  <  .riiliii.m  «|ii.u  l/ilrs. 
2(J<)  ft'Cl.  |i's|mj4  nil  llir  All  li.r.m 
^t,\\\\\r. 

i.  Slim  I. Ill  silii  n  Ills  liiiH'sli  nil's 
.iinl  i|ii.ii  l/i(i's.   ;,|()  Icfl . 

\.     |),iikri        liiiH'sti  mrs.       iiis|\ 


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brown  aiifl  floloinilic  at  base,  hliu.'  coinijact  and  pure  mi  lop, 
240  Icct.     ('ilicsc  arc  Lower  ('arbonilcrous.i 

4.  CarbfJiiifcrous  clays  and  sbalcs  and  tbin  Ijudded  liino 
stones,  425  feet.  Tbc'sc  bclonjj^  to  the  Weber  ^nifs  i  Midrlle 
(arbonilerous). 

5.  A  series  of  \ariej^'ated  fjj-reen  and  red  sandstones,  claxs 
and  shales,  some  limestones  and  vv(\  sandstones  ol  the 
I  pper  (  arbonifcroiis, 

6.  Heax'v  bedded  red  sandstones  (Triassic). 

Above  these  asjfain  are  several  thousand  feet  of  Cretaceous 
strata,  up  to  (he  base  ot  tlie  Laramie  coal  l)eds.  ('I'he  (reta- 
ce  )us,  however,  and  the  Jurassic  do  not  re;. I  imnicfliately 
upon  the  /j^ranitei. 

Ih'orih'.  ()n  As|)en  Mountain  is  a  bed  ol  "white  poiphx- 
rv  "  (fiiorite)  in  the  black  shales,  60  to  100  feet  above  the 
top  of  the  blue  limestone.  It  is  2A0  leet  thick  on  the  slope 
back  of  town,  but  I  hickens  consideiably  to  the  south,  and 
is  traceable  to  Ashcroft.  It  apjiears  to  extend  also  across 
the  \alley  of  Koarinj.,'  l'"ork  to  Smuja^/.,dei  Mountain.  Small 
inlrusi\f  sheets  also  occur  in  the  lower  cpiart/iti-s  near  the 
point  of  Aspen  .Nhjuntain  and  on  the  east  lace  ol  Kichm'-i)f| 
llill. 

As  affected  b\  the  Sawatch  upheaxal,  these  beds  wrap 
around  the  Arcluean  mass,  resfinj^^  a^^ainst  or  dip[)in,t(  away 
from  it  at  varyinjr  anj^des. 

The  (piartzites  and  limestones  cross  the  \alley  ot  Roaring 
Fork  from  Smu^jj^U-r  Mountain  to  .\s|)en  Mountain,  strikinj.f 
northeast  and  southwest,  dippini^  mut hwi.'st.  'I'he  a  11^4 le 
ot  (lip  is  about  45  .  varyin;.;  fiom  a  minimum  of  30  to  a  ma.\i- 
mum  of  60    in  '*  Hats  "  and  "  ste(!|)s." 

rill.   (tUI.    linlUKS. 

The  lower  carboniferous  "blue  limestone"  is  com|)a(  t. 
homojj;eneous  and  composed  of  pure  carbonate  of  lime.  The 
"  brown  "  or  "short"  dolomitic  limestone  is  of  a  dark  s^ray 
color,  linely  crystallint-,  finely  f^ranulated  and  tra\t  rsed  in 
every  direction  by  a  network  ol  minute  \einlets  containinjr 
iron  salts,  which,  when  oxidi/ed,  color  the  surface  a  rusiv 
blown.  The  oxidation  a  Ion  j.^  t  hese  minute  veins  makes  t  he 
rock  break  easily  into  dice-shaped  fragments  ^i\in^  t  he  rock 
a  "crackly  "  structure,  hence  its  local  name  of  short   lime. 

(hi'  Diitrihiilion.  The  outlines  of  the  ore  bodies  c mnot 
he  detected  by  tlie  eye,  owinjj;  to  the  tjradual  transitio-i  troni 
ore  to  country  rock. 

The  ore  is  not  conlined  to  the  brown  dolomift;  below  (he 


i6(; 


S()-c;ille»l  coiUacl.  hut  several  ore  bodies  extend  20  or  ;o  leet 
al)ove  tliisc'oiitaet  into  tiie  blue  limestone  and  in  some  cases 
follow  the  lines  ol  cross-fracture  cnfiri'i\-  across  the  l)lue 
limt'stone. 

The  ore  is  not  confined,  either,  to  a  d"linite  plane  or  con- 
tact between  two  dissimilar  l)eds  ot  Jiuu-sione  and  dolomite 
Irom  which  its  solutions  ii.t\e  ealen  into  tlu"  underK  inj,^ 
do|(»mile,  lor  in  the  first  place  there  is  no!  one  si nj^jle  con- 
tact, but  manv;  and  if  this  so-called  contact  const ilules  an 
essential  condition  o|  ore  deposition,  theri-  is  no  icason  why 
it  should  be  conlini-d  to  tin*  one  and  not  lound  in  t  lie  others 
where  the  rocks  h.i\e  the  same  cc  imposii  ii  .n.  Ai^ain.  on-- 
bearirif^  sol ut  ions  would  not  he  lil<el\  to  eat  upwards  tui  an v 
^reat  distance  Irom  the  contact  plane  it  the\  enteied  the 
befls  al<  lUfj;  1  his  pi. me. 

I'his  s(i-c.dled  coniact  plani'  is  well  delined  on  S|>.ir  Rid;.fe 
and  continues  down  with  the  dip  in  the  underj.jround  work- 
\i\jj;,  hut  ore  bodies  cicc  iir  ah<i\f  and   helow  it. 

The  Kick  thus  minerali/ed  is  doloniite  in  most  cases,  hut 
it  is  none  the  k'ss  al)o\'e  the  true  heddiny;  |>lane  called  the 
contac  t. 

In  ot  her  |)ai  ts  t  heic  has  been  tract  urinj.;  across  the  he<ls  as 
shown  h\-  a  vertical  breccia  of  limestone  fraj.jments  with  a 
cement  of  iron  oxide  and  manj..janese. 

( )\  11  t  he  ori'  bodies  aie  lines  of  open  cavities  iollowinj^ 
the  lines  of  cioss-fracture.  throuji;h  which  the  ore  solutions 
passed  which  deposited  the  ore  bodies.  These  ca\fs  are 
now  beinj4  hollowed  out  by  water  descendinjj^  from  the  sur- 
face dissoKinjj;  the  limestone  in  the  roof  and  llowinjf  oil  alon;.j 
the  floor,  di'|)osi!in<.r  a  mud  of  silici,  alumina,  lime.  ma}.^nesia 
and  iron  oxide. 

Hence  this  contact  is  not  necessarily  the  only  ore  channel 
of  iIk'  district,  and  other  channels  mav  hi'  sou^dit  tor. 

I'ortioiis  of  the  ore  bodies  have  been  formi'd  by  solutions 
percolatinj.j  throiij^'^h  cross-fractures  and  spreadinu:  '>iit  be- 
tween the  p.nallel  heddintj^  planes. 

This  would  happen  if  these  solutions  derived  tlieii  metals 
from  tlu;  overlvinj.,'^  |)orphyry,  for  it  is  separated  trom  the 
limestone  bv  arjj[illaceous  shales  which  wmdd  be  impervious 
unless  fracturi'd  across  the  beddinj^.  The  analysis  of  tin* 
lime  mud  at  bottom  of  the  cave  shows  by  its  preponderance 
of  alkalies,  which  do  not  exist  in  the  composition  of  either 
brown  or  blue  limestone,  that  the  waters  flissolvinjj;  it  came 
from  the  port)hvr\.  The  waters  brouj.jht  both  alkalies  and 
sil  ca  from   tlie  porphvry.  and  probably  the  iron  and  baryta, 


r^ 


J 


iMil.nMI  I  I/A  I  liiN. 

Tin's  is  a  scrondaiv  process  upDii  llu-  blue  limcstniic  l)y 
inagiusian  \v;iliis.  which  is  proM-rl  by  irn'j^nilar  t<)ii>j;iu's  of 
doloiiiito  cxtiMulinjj:  iij),  into  and  across  the  blue  linicstoru'. 
The  It'iiticulai  bodit-s  in  tin-  Diirant  clitl  point  to  the  same 
fact.  'I'hf  crarkly  stiiKliin'  ot  ihc  blown  hnic  results  lioni 
the  replaceivjeut  ol  a  molei  iiie  o|  lime  by  a  inoiccujr  of 
maj^Miesia.  iiu'oh  in^^"-  also  a  contraction  in  \ohiir,r  ol  the 
rock  it>cll,  which  W(»iild  cause  it  to  sepaiair  \\\  anj^ular  Iraj^- 
Mients.  the  intersections  rilled  by  mati'rial  more  soluble  than 
the  rock  itself. 

The  maj^ne-ian  waters  may  have  been  connected  with 
those  which  broni^hl  in  the  vein  materials. 

In  the  ore  :>odies  the  partially  minerali/ed  rock  on  the 
borders  ol  (he  ore  is  chaii;.^ed  to  dolomite,  Iu-ihc  dolouiili- 
/ation  either  preceded  or  accoinpaiiit'd  ore  deposition. 

Mr.  l'!ii!iMons  su^'i.i^est s  ,\s  />/ (>/>(t/</7///i  <;  onl\',  that  the  por- 
phyry mliusioii  preceded  tlu-  laiiltiii;^  ; 

That  lilt'  ore  deposit  followed  the  intrusion  ol  porph\  ry 
and  :.)^o  the  inincipal  fanllini,'  mo\ements  ; 

That  small  moxeinenls  ha\'e  taken  place  in  recent  times 
both  in  the  strata  and  coiitainefl  ore  bodies  since  the  o.xida- 
tion  of  the  latter  ;  thai  at  the  time  of  the  ^n-.\\  fault  int,'.  the 
beds  mav  ic;).  have   attained  entirely  their  presi-nt  |)o>,ition. 

In  the  vicinity  of  Asptn  .Mountain  ore  boflies,  the  strata 
appear  to  ha\e  been  s\nchnallv  fohh-d  and  faulle(l  between 
the  main  Archa'an  area  on  the  t-ast,  and  a  mass  ot  granite 
at  the  westtMii  e.xtiemity  of  the  mountain,  thus  pioducinjf  a 
second  series  ot  oppo^itelv  inclined  beds,  also  crjutaininj.^  a 
few  ore  l)odies.  Intrusions  ol  altered  erupt i\e  diorite  o( cupy 
a  prominent  position  in  the  interveninj^  trough  and  m.iy 
ha\e  seriously  faulted  or  dislocated  the  strata  in  the  dejiths. 
The  bulk  of  the  Aspen  ores  are  lai>;«ly  o.xirlalion  produt  ts 
of  ai>,nMitiferou^  minerals  with  trm-  sil\  t-r  minerals,  associated 
with  cahspar  and  baryta  ;  it  is  a  "dr\'  ore  "  ro<)uiiin).r  to  he 
mi.xed  with  silicious  lead  ores  before  it  can  be  Heated. 
Such  rich  ores  as  polybasite  and  brittle  siher  occur  also. 

A  jj^reat  deal  of  the  ore  consists  ol  line  jr mined  stei  1  j^alena. 
\'erv  rich  in  siKer. 


ASIM'.N    AS    A    I'KnsiM'.f    I  |\(;   ckofNK. 

.Xspi'ii  ajj^ain  is  an  example  of  a  rej,don  that  had  often  been 
sl-hii)iiiii  nwv  by  the  piospi'i  tor  and  ab.mdoned  belmc  the 
final  tlioroiif^h  prospecting;  re\-ealed  its  j^reat  riches,     \ears 


171 

^.\fr^>  sonic  |)r(ispi'(t()is  fomul  sijj;ns  dI  •  ll.i.it  "  ;in(l  •  blnssDin  " 
cropping'  out  iiiuk'i  the  l)liu'  liiiR'stoiic  ol  Spar  Kidjj^i*.  They 
{■\ru  went  so  tai"  as  to  sink  a.i  iiuliiu-  ol  a  hundit'd  l\  i-t  or 
nioic  l)nt  thoiij^di  tlir\  louiid  oic,  its  chaiac  tn  was  so  low 
ijfradt'.  that  the  mine  was  lor  a  I<m^  time  shut  flown  and 
piactically  abandoned.  'I'hcn  an  en  trip  lis  ini,^  indi\  idnal  toii- 
<';'i\i'd  tlu-  idea  o|  boiin;^  down  on  the  ^lo|)ln^  hack  ol  the 
hniestoiie  in  the  adjoinin^j^  X'allejo  j^jiilch.  to  tap  the  ore 
hod\ ,  alread\'  disro\»Ted  alonj^  jlie  oiitt  loppinj^,  on  the 
iindeisidi-  ol  the  lini-Ntone.  .\(  about  150  leel  di-i'p  the 
hmestonc  was  pierced,  and  an  enoiniouslv  larj;e  and  riehore 
l)ofly  was  disco\(i  -d.  hnnu-diateU  ,  the  oiij^inal  lota'.ois 
bcf^Mii  aj4;ain  with  all  Mxed  to  pu>h  on  tlu-ir  incline,  and 
then  oiij^rinated  the  celebrated  "  apix  and  side  lin«'  '  lawsuit. 
The  oiijj^inal  locators  had  the  apex  on  the  outcrop.  I  hev 
therefore  claimed  the  whole  moun'ain.  .i.iil  tried  to  rhive 
out  the  side  line  men.  I*'inally  a  compromise  was  cJ'ertt'd, 
hut  that  t)orin^f  d<wn  on  the  b.ick  ol  the  lina  tone  and  its 
(list  o\  eries  l«'d  iini!  fdialelv  to  an  ;'rm\  01  jirospect'  rs  ex- 
aminiiij;  tlu-  nroMntain.  and  it  was  astonishing.;  how  ni.iiiy  ore- 
deposits  were  (hsco\tief!  Ml  a  retrioii  that  wis  siip|)osr(|  to 
ha\e  bee. I  nrospe*  .  ed  aiul  -j:i\'en  u|)  as  no  jjjood.  ( )|  course 
Aspeii  is  an  .xamn'  •  ol  "  >  /,  ///it:s.\a'///t  </i/>///."  .\  ditiu^t-rous 
piecedi  .  '  and  e!\couraL;emeht  to  that  olten  ruinous  policy 
ol  rum.'  ^  I'Mi^j;  cross-cut  tunnels  to  i  iit  an  ore  horly  at 
de|)th,  will'  ii  his  only  |>ro\ed  indilferently  j^ood  n«'ar  t!ie 
siirlace.  I".  Ihi-  tallacy  we  ha\-e  beloie  alluded  to,  o|  the 
improbable  [o  ot- dtilify  of  "  1  ichnes',  increasiii;.^  with  depth." 


\\    l-.N  Wll'l 


1!     I'KDSI'IC  IINC,. 


Now  Mi|ip(»sin,t:  our  pros  •untor  was  the  lirsi  i.mii  to  .iiter 
that  re>4[ion  years  aj,'o,  \Vh.  t  simis  weretheri-  to  Nad  I  :ii  to 
think  it  was  a  ^jood  piospeclin^  ^;rounfl  .'  Supposinj;  liini  tt^ 
be  laiiK  \'Msed  in  ).,'eol (»•.,",  \u'  would  have  not"'  "d.  as  he 
<-ame  deiwr.  over  the  Sawatch  raiij^e.  that  the  I'aleozoic 
strata  he  hafl  obserxt  d  as  ore-bearinjj[  at  Lead\ille,  out- 
<roppefl  also  on  this  western  side,  tojj^i'ther  w  ith  the  "  blue 
limestoiu' ;  "  secondly,  he;  would  have  noticed  tlu'  nn'sence 
ol  |.irjj:e  massi's  ol  cntf>(ive  rock  ci instituting  the  I%1k  ranj^e  ; 
fhirdlv,  he  wo'.i!'!  ol)S'Tve  the  u'j;j,,n  was  much  disturbe-', 
that  the  strata  were  intt-nseis  folded,  and  intenselv  laiiUed. 
All  these  sijrns  lie  would  h  i\'e  conssder'-d  likeh-.  TIumi 
after  following;  up  the  \arious  creeks,  he  would  select  such 
spots   as   where    he    saw    th'    massive    blue  liinesioiu-  out- 


Ht  XvrVCa-fHCMMI 


Miliiiif 


! 


I'  I 
h 


7:: 


ill-  utjiilfl  re;i(lilv  liiul   this  hfd  tiom  its  U'lation 

(•     Woulfl 


II 


to  till'  t,n;mit»'  aiui  Cainl)!'!;!!!  (|ii;ii  tzitc  hi-low 
look  Inr  pl.ii  I's  uhcMX-  poipliyiv  w.is  iiilnidcd  into  the  liiiu- 
stouc  or  whciL'  jr»c;it  masses  oi  it  lay  al)o\'c  or  in  \icinity  of 
the  limfstoiir.  This  woiihl  prohahly  lia\t'  led  him,  on  iirar- 
inj,r  AspL'ii  Mounlaiii  to  ^iw  that  iiioiiiilain  moic  than  a 
[>assin^  look.  He  would  notice  that  the  strata  on  As|)eii 
Mountain  were  \<'ry  mueli  disturbi-d  and  laulled.that  a  spur 
of  granite,  (juite  out  of  place,  came  rij^ht  up  throu;,jh  the 
middle  of  tlu-  mountain,  that  strata  were  pitchinjj;  in  \arious 
directions  oH  from  this,  aiu!  moreo\  t-r  that  in  the  lap  of  this 
lault-fold  was  a  \ery  thick  hi-d  ol  por|)hyry.  Me  would 
obsei\'e  the  line  of  chanj^i'  from  tlu'  hlue  limestone  to  the 
dolomite,  and  at  that  line  he  would  have  piospeiled  and 
found  and  followed  up  the  "  l)lo>soni  "at  t  he  line.  consi>t  intj 
of  calcite  aiul  haiNta  runninjf  in  a  rusty  line,  liki-  the  out- 
crop of  a  Coal  seam,  all  up  the  side  ot  Spai  (iulcli  and  >o  \\c 
would  ha\i'  disco\ered  the  ^neat  Aspt-ii  oie-di-posils.  .md  hv 
followinj^  up  the  indications  alonj^  tlw  outcrop  and  loratinij 
claim  after  claim  as  aloiijj;'  an  outcioppini;  coal  seam,  he 
couid  h  .\X'  secured  |uacl  icall\- 1  he  whole  ••a|)i'.\  "  of  the  hill, 
and  1)( /ome  master  of  the  mountain  and  all  it  contained; 
but  had  he  known  then  the  liti}.,^aiion  of 'side  line  and  apex" 
that  was  to  arise,  he  should  ha\e  tjone  lurther,  and  located 
claims  co\erinjj^  the  si<le  line,  on  the  l)a(  k  of  tlu-  slopinj^ 
limestone  rid^e.  leadinj^'  down  into  X'alli'jo  },'ulch.  Hut 
aj^ain  he  mij^hl.  like  the  original  liist  disco\erers,  have  be- 
come disheaiteui'd  with  his  lind  on  ti'slin^'  the  outcroppinj,r 
{jre  by  assay  or  mill  run.  and  lindinj.f  it  so  low  jj^rade  lu-ar 
tlu?  surface.  ( )n  i^eneral  principles  in  this  respect  he  woulfi 
lia\e  been  rijj;^ht. 

Now  ha\iii^  Ihorouj^hl)-  explored  the  little  .\spen  .Moun- 
tain, he  would  observe  that  much  the  same  tormations 
{  rossed  the  creek  and  entered  into  Smu^^lei  .Mountain, 
thou<.,di  niucdi  obscured  1)\  heavy  jj^lacial  drift,  lb-re  he 
mijj^ht  lia\e  located  fresh  claims  on  this  hill. and  bt-come  the 
owner  ot  the  celebrated  Smi'jux'i"'.  Key;e.it  and  other  mines 
with  their  untold  wealth.  Thence  he  mi<.,dit  lia\<'  (ontinued 
his  sucifssful  tri|),  and  followed  the  same  so-called  •con- 
tact" outcrop  for  miles  on  to  Asluroft.  It  must  be  re- 
membered here,  howexer,  that  in  loiatinj^all  these  claims, 
whilst  the  prospector  ma\  drive  bis  location  stake  at  e\"ery 
i.5(K)  leet,  he  is  retpiired  within  si\t\-  da\s  after  location,  (o 
(W^  a  ten  toot  hole  in  each  location.  .\s  this  ma\-  be  a  little 
dillicult  tor  him  to  flo  he  tjenerally  enlists  others  in  his  enter- 


> 


173 

prise,  l<)  assist  him.  ;iii(l  fiiUTs  somr  ol  tlic  cLiii-.i,  m  tlicii 
namrs,  to  pn-voiit  tiic  (ii>(i)\crii's  hi-iiij^;  iiim|)»(l  i)\  ;•  IhikIi- 
of  piospt'itois  \vhi>  press  ill  as  soon  as  an\  tliinjj;  is  tMimd. 
(iixxl  a(i\i(i'  to  a  prospector,  is  to  kroi)  \crvslili  ai-.d  ■imim" 
about  his  (h'sco\»-rifs  until  \\v  has  wt-ll  Sfciircfl  thtin,  .ind  to 
he  very  careliil  how  he  ••  « ipeiis  his  iicad  '  to  aiiv  one.  ( "oiii- 
inoiily  a  prospt'ctoi  u  ho  has  '•struck  it,"  comes  into  to\v!5. 
tills  up  w  ith  whiskey.  "  blows  it  in."  and  I  hen.  "  blows  it  oil  " 
ail  over  town  .lijout  his  discovery,  and  is  elated  to  find  him- 
self the  hero  ol  l!ie  hour.  Tlie  r<'-nlt  is.  betore  d.iylii^ht  the 
lollowinj.,^  mornin<.,^  a  hundred  men  are  chasi'ij.-  '.i/e  another 
in  the  direction  ol  his  discovery,  and  bi-lore  a  da\  or  more 
is  over,  the  mountain  is  co\erefl  with  locations  as  close  as 
jj^ra\es  in  a  cit\' churchyard,  and  in  a  week's  time  these 
locations  ;'.re  covered  attain  by  a  seiond  layirr.  as  tlie  >a\inii 
is,  "several  feet  deeji." 

A  boom  tollows.  The  olfscourinj^s  of  the  counlrv  pour  im 
witi)  the  saloon,  dance  hall  and  j^andjliny;  hell  element.  .\ 
mur<ler  or  two  follows.  Lynch  law  takes  a  hand.  Tln-n  a. 
horde  of  real  estate  men  come  in,  and  lots  are  sold  at 
fahnh.us  [)rict;s,  and  the  town  is  inllated  with  a  po])nlation 
and  everythinj^^  else  usuallv  lar  above  the  capacitv  "f  tin 
mines  to  su|)port.  A  c:ollapse  follows,  and  a  steady  retreat 
of  hollow-eyed,  disajipointed  adventurers.  In  time  the  town 
and  cam|)  assume  their  lawful  ])roporlions  and  busniess 
settli's  down  to  its  lawful  regime. 

Whilst  all  this  has  beiMi  j.joing  on,  aufl  amidst  all  the  fuss, 
and  bustle. md  "■  hoora\  in/.^  "  ol  real  estate  "  boonieis  "  and 
so  forth,  some  prospectors  have  been  <|uietl\  tryinj.^  to  fol- 
low up  the  first  desirable  infiications  into  the  neitjhboriny 
rei.!;^ion,  lesultin.ii  olten  in  .m  extension  ol  the  ore-l)eai  int' 
rej^^ion.  Some  of  these  locations  are  "bona  tide  "  and 
valuable.  ()ther  "holes  in  the  j^^round  "  aie  (\u^  < 'W  the 
merest  |)rete.\t  of  indications  to  catch  tlu:  i}.^!),  ,r.mt,  atl- 
\"enturous  tendi-rtoot  ca|)italist  puiihasers,  or  "suckers." 
An  investor  j^^oini^  into  the  camp  at  such  a  time,  !in(U  a 
fabulous  price  placed  on  e\erv  prospect,  whether  i^cnuine  oi 
false.  .\s  a  |)ruflent  man,  he  either  lieats  down  mk  li  prices., 
or  cotK  hides  he  will  visit  the  camp  a  little  laler,  when  the 
excitement  and  inllation  has  j^oni-  down,  and  when  thintjs 
are  on  more  of  a  business  footinj^,  anfl  somethinj^;  like  the 
real  value  of  the  camp  has  been  found  and  proved.  ( >t 
course  in  such  a  jj^.unbliny  speculation,  by  such  pru<lencc 
and  delav  he  mav  lose  a  luckv  chance,  but  he  has  preserver! 
his  prudence  and  es<apefi  beinjj^  wofullv   l)itten. 


i;    ) 

I'   * 

u 


If 


) 
t 


174 

I'd  haps  in  a  inoiitirs  time,  the  disci  >\riii's  aif  finiiid  to  he 
intTcK  stipfilicial,  I  he  hnum  iilti'i  ly  lollapst-s,  and  I  lie  drcai  v 
•sij^lit  is  stjcn  a  litllr  lalcr.  ot  a  flesulalc  xillaj^^c.  witli  lianir 
houses  an<l  \n^  cahins.  and  possibly  a  mill  or  Iwo.  tor  mills 
an:  suii-  to  lollow,  lyinj^^  in  wreck  and  ruin,  a  home  lor  the 
owls  and  the  bats;  or  else  the  j4:enuine  discovery  |)roduccs 
one  oi  two  minis  and  suppoils  a  handlul  ol  population 
lej^fitimately. 

.Ajjain.  a  rejjion  like  Aspt;n  may  flisclose  a  limited  number 
of  \'i'r\  licli  ore  deposits,  hut  sullicienl  to  snppoif  ;ind  nus- 
lain  a  t.iir  sized  town. 

Hut  the  most  imnortanl  and  most  lastin-;^  discoveries  of 
al!  are  of  areas  profuuiny  an  immense  (piantity  of  low  ^^rade 
ore  such  as  l.ead\  ille,  This  j^i\'es  an  opportunity  for  ;i 
^reat  number  ol  mines  iiid  loi  (he  support  ot  a  larj^je  and 
]M'i  lu.iiient  town. 


KXAMlNlNCi 


CHAITI'K  XI 11. 

AND     SA.MIM.INC.      MIN1N(, 
PROSIMXTS   OK  MINKS. 


I'KolM.RTIKS, 


A  [uospector  ma\  be.  or  bei  onie,  a  "  mining  i\\pert  "  and 
1)0  called  upon  lo  make  examinations  of  mininj.j  |)roperties. 
whetlu'r  prospects  oi  dt'\('lo[»ed  mines,  so  a  lew  snj,fj^est  ions 
jnay  [)ro\e  useful. 

Mininjji;  properties  of  the  precious  metals  are  jrenerally  <d 
two  kinds,  those  coiilaininji  ore  dt  jl()^i(^  in  place,  snch  as 
tissur-  veins  and  blanket  diposils  and  |)lacers,  the  latlei  be- 
\\\^  ^fold-ln-ariiifi;.  In  both  eases,  and  especially  in  the 
former,  (he  charactei,  posilinu  ;»n<l  olhei  lel.itions  of 
properties  are  inlinitely  varied,  so  that  no  hard  and  last  ride 
can  be  tfixcn  to  suit  all  cases;  certain  rules,  howi-ver,  will 
jj;ener.dly  app.ly. 

A  minin^r  i-n^ineer  recei\<-s  a  letter  hom  a  comp.iny  tell- 
inj;  him  tojjro  to  .such  and  such  a  country  or  rej.,Hon  and 
examine  and  report  on  a  certain  proix-rtv  that  has  been 
olfi-red  (hem.  Such  a  mandate  is  usually  ac(  «)inp;'nied  by  a 
letter  or  report  from  (he  owner  or  parties  olTnin;.;  (he 
property.  j,(ivinjj[  (he  (»wner's  rlescriptiou  of  (he  same,  orelse 
the  n-port  of  souje  expert  on  it.  As  ;•.  j.fi-neral  rule  such 
reportsj,d\e  the  most  favorai)le  view,  and  in  soniecases  nuist 


/-> 


bflakrn  "<  // 


in  ijriif/ii  SiU/s. 


In  III 


f  minmj^M'iij^nufci  thev  yiv  t- 


somr  suit  o|  all  idiM  as  ti>  what  llu-  puipiity  may  Ik-  liki' 
As  to  its  \aliM',  flc,  t hat  lie  proixiscs  to  liiid  nut  tni  hini- 
sfll.  'riif  (  ompaiix  sDiiifl  iiiu-~  asks  liiin  In  fxaininc  wit  li  a 
\ir\v   t<»   Nt'iilyiiij,'  "i    modify  iujr  ,,r  <  nnl  iadi<  liiij^^   such    ic- 

|MlltS. 

Thi"  it'j^noii.  the  (  tuinl  ly,  the  tharaclfi  o|  Hu-  (li|)o>i|s,  |  he 
loral  coiulilions.  may  in  all  prohahility  he  comparatixcly  new 
or  stiaiij^T  to  him.  I'rior  to  slaitint,'  he  mav  makf  iiii|uirics 
ill  miiiiiiL; circles  it  aii\  t hiii^'^  is  known  about  the  icj^iniior 
distiiit.  It  thrri"  an-  any  puhlishcd  mininj^;  or  jri-oloyual 
reports  (»i  maps,  he  will  consult  these.  j-inalK  he  st.nlsdut 
with  as  jilth'  ha)4j.;.i^c  as  possihie.  usual!)  .1  small  h.md  li.ij;;, 
('onlainin^  .1  h-w  ncct'ssaries  ;  a  tapelini',  j.;eo|()j.rical  pick.. 
clinometer  and  compass  and  note  01  sketch  honk.  Ilisduss 
is  gcneially  a  suit  o|  (oiduroys.  lealhei  j^aiteis  .md  sir..u;.{ 
hoots. 

.\s  he  enters  the  rej,don  h\  rail  01  mi  h,»i  sehack  he  notices 
the  lu.iiii  j^folojj^ii  .d  tealuies,  uhi  lliei  the  io(  ks  are  j^i.iiiit ic. 
sedimeiilary.  01  eiupli\e.  I''iiiall\  he  hmcIu-s  iIm-  (amp. 
calls  im  the  ownei  oi  supei  inleiideiil  and  rides  up  uilh  him 
to  \  isit  the  mine.  Il  he  shoidd  "  la\'  o\  t'l  "  lot  the  allri- 
iiooM  in  the  \  illaj.ji\  he  may  as  indire(  tl\  as  possible  tr\  to 
pick  up  any  tjossip  there  mav  he  alloat  relatinj,^  to  the 
property,  lie  is  at  oiu'e  impressed  \vith  the  accessihilit v 
or  inacct'ssihililv  ot  the  pro|)erly,  ami  estimates  the  pioha- 
l)le  cost  ot  lninj.^iii)4  down  the  oie  to  the  mill  or  to  the  i.iil- 
way  track,  and  ohsei\es  the  proximity  1  u'  ahseiu  e  ot  timher 
and  water  powi-r  .\t  last  he  rea(  lies  the  mim-,  iliiies  ai  I  he 
hoaidiiiL,'  house,  and  is  iheii  takt  11  o\ci  the  |)ieniises  l)\  the 
superinleiidenl.  Mis  llisl  attention  is  diie(  ted  |o  the  sur- 
face character  <>(  the  piopiilv,  its  lopojj^raphv ,  whether 
roljiuj.;.  smooth  or  pr«'cipitous,  wheihei  it  is  hij;h  aho\c  the 
\  .illi'y  tir  m-ar  (low  n  to  il.  whether  the  mine  is  hij.,di  or  low- 
as  rt'jji'ards  the  water  le\tl  (U  drainaf^'e  system  ol  the  iieii»h- 
hoihood,  whether  the  piopeilv  is  con\  ('nieiilh  situ.iled  tor 
workiiiff  the  mine  and  transport inj,;  the  oie,  etc. 

Accessihili;  V  is  an  important  matter.  In  some  reyions,. 
such  as  in  tJie  San  ju.in  distiict  (Color. idol  lor  e.x.imple. 
mines  aiul  prospect  holes  an-  sometimes  on  the  top  or  sides 
ot  mountains  01  pii-cipices,  thousands  ol  leet  aho\i'  the 
\allev  below,  located  at  spots  oiu' wmild  t  liiiik  (mly.iiieayle 
Could  reach  ;  prospect  tunnels,  too.  .ire  diixcii  wliei»'  there 
appears  scarcidy  a  h)ot  hold  for  ;  stpiirrel.  No  spot.  howe\  t-r. 
seems  too  inaccessible  lor  the   juospe' loi.     .\(  a  ijlaiK  c  I  he 


-^ 


176 


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177 

viiKint'i-T  s«'fs  that  in  a  piMpnts  NJliiatrd  in  mk  li  a  icj^iun, 
;u'rr>sihility  is  mu' i>l  the  tiist  and  oltcn  iiimnI  !■  ii  luidable 
pi°itl>k-ius  to  l»r  ('i>lisi(lrt'«'(l. 

'I'm  sonu'  ol  tlii'sr  mini's  air  loii^  /.i^/.;\^  tiails  cnl  in  the 
side  of  tilt*  inonntain.  Tht-  (-n^^int■(■^  calt  iilatfs  how  nuuh 
tlif  iiwncrs  «)|  (lir  (l<»nkcv  <ii  "  hnrm  "  i  rain  will  cliar^if  •" 
l)rin^' that  oil"  down  t<»  tin'  valley  or  mill,  lie  ai>;nr«  ih.a 
a  mint*  at  that  almost  inacccssihir  hci^rjii,  on^^ht  to  carry  a 
j^rood  (It'll  ol  pii'liy  hi^h  ^fiadt'  oi»'  to  pax  ••\»'n  lor  traiisnor. 
lalioii  h\  till'  '■  hiiiios,  III  aloiu'  ihccost  ol  height  altcr- 
wards  to  distant  sim-ltiii^r  works.     ( )ii  ihr  other  hand  a  mine 


I 


ey  or 
'   un 


■ • ' ^    ■ '■••  •    --••■ 

whose  w«»rkin>^'s  oiu-n  ont  within  eas\  .ict cs*.  ot  ihr  \  ;i 

railway  tra<  k.  (  onid  allord  lo  c.iriy  le>s  vahiahle  ore 

lIuTC    is    timhei    and    wati-r    power   to    he   eonsiden-d.    the 
lormer  lor  timherinj;^   the  workings  ol    the   mine,   the   latter 


l"r  sneli  a  mill,  under  a  developed  piopnlv  ;  11  there  he  a 
mill  oil  tin-  |)ieniises.  he  will  e.N.itniite  and  report  on  its 
capaeitN  and  siiitahility  tor  tieatini,'  the  oris.  A  mill  site 
must,  ot  C'lnisc.  he  selei  ted  (lose  to  some  water  power.  In 
soiiK'  diNliiets  there  is  a  Mipirahiindam  e  ol  water,  in  others 
;j  serious  lack  ol  it.  or  the  supply  is  nK'af;;re  at  ceitain  sea- 
sons, or  is  lio/fii  lip  in  winter.  Some  mines  are  <piile  (ii\. 
hut  j.fene  rally  I  hey  will  supply  iiionj^h  mine- water  liom  I  heir 
workiiiLfs  to  allord  steam  Dower. 


IMAGE  EVALUATION 
TEST  TARGET  (MT-3) 


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Photographic 

Sciences 
Corporation 


23  WEST  MAIN  STREET 

WEBSTER,  N.Y.  14580 

(716)  872-4503 


'^^:^' 


"^f^ 


iV 


178 


obtain  an  incorrect  estimate  of  the  average  run  of  the  mine. 
Moreover  in  some  cases  it  is  well  to  be  on  the  look  out,  lest 


these  points  to  which  special  attention  is  called  by  the  miner, 
be  previously  "salted"  or  "put  up"  for  the  expert,  and 
charged  in  various  ways  by  rich  ore. 


179 


Haviiif^  traversed  the  workiiifrs  and  obtained  a  general 
idea  of  tlie  position  of  the  \ein  and  ore  bodies,  and  taking 
an  inA'entory  of  the  amount  of  development,  length  of  drifts, 
shafts,  etc.  (the  latter  he  can  obtain  from  a  map  of  the  mine 
in  the  snperintendent's  office,  a  copy  of  which  he  will  send 
to  his  company)  he  asks  the  superintendent  to  leave  him  and 
his  assistant  and  vacate  the  mine,  as  he  does  not  wish  any 
one  except  his  assistant  to  be  with  him  whilst  he  is  taking 
samples  for  assay. 

SAMPLING. 

Now  begins  his  hard  and  most  telling  work,  the  time  and 
labor  depending  \'cry  much  upon  the  size  and  amount  of 
development  in  the  mine,  or  the  degree  of  accuracy  neces- 
sary. Taking  a  large  strip  of  muslin,  he  cuts  part  of  it  up 
into  small  pieces  about  the  size  of  a  pocket  handkerchief, 
these  an-  to  contain  his  samples  for  assay,  when  quartered. 
Then  he  takes  the  remainder  of  the  muslin,  or  better  still  an 
ordinary  candlebox,  this  to  catch  the  mass  of  small  frag- 
ments he  detaches  from  the  vein  with  his  pick. 

Now  with  a  light  pick  or  with  a  chisel  and  hammer  he 
begins,  either  from  the  entrance  or  end  of  the  tunnel,  to 
detach  small  portions  of  the  rock,  cutting  a  rough  groove 
across  the  vein.  Sometimes  the  tunnel  occupies  the  whole 
width  of  the  vein  in  which  case  he  will  have  to  make  a  cir- 
cular groove  clear  around  the  tunnel,  across  floor,  roof  and 
walls  as  shown  in  Plate  XCI V  ;  the  fragments  from  his  work 
drop  into  the  candlebox  or  onto  the  muslin. 

vNccording  to  the  length  of  the  workings  or  the  need  for 
great  accurac3%  he  repeats  this  operation  at  intervals  which 
may  be  every  5  feet,  10  feet  or  20  feet ;  at  intervals  of  say  20 
feet,  he  masses  and  mixes  together  all  the  samples,  breaks 
them  up  as  tine  as  he  can  on  a  shovel  and  divides  the  result 
into  four  parts,  throws  away  three  parts  and  retains  one. 
This  he  reduces  to  a  fine  powder  and  wraps  up  in  the  small 
muslin  pieces,  ties  it  up  and  seals  with  sealing  wax,  marking 
on  it  the  number  and  other  notes,  such  as  10  feet  from 
entrance,  etc.,  with  an  indelible  pencil.  This  work  he  con- 
tinues till  he  has  reached  the  end  of  the  tunnel,  which  if  it 
be  100  feet  long  will  give  him  from  20  feet  intervals,  live  little 
sacks  of  powdered  ore  for  assaying.  As  a  check  upon  this 
work  and  for  reference  in  case  of  any  accident  to  or  any 
tampering  with  his  samples  in  transit,  he  Avill  occasionally 
take  a  "  grab  "  sample  from  his  broken  rock  before  quarter- 
ing it.     Here  and  tliere,  too,  he  may  take  a  chunk  of  some 


St 


■1 1 
.ill 


•I ;(: 


i 


!« 


i8o 

peculiar  rock  such  as  a  porphyry  or  some  peculiar  streak  in 
the  gangue,  these  he  will  put  in  his  coat  pocket  anrl  keep  on 
his  person. 

It  is  sometimes  important  in  a  vein  to  find  out  what  rock 

or  portion  of  rock 
carries  the  most 
x'alue.  For  instance, 
on  one  (occasion  we 
examined  a  vein  said 
to  carry  gold  clear 
across  its  entire 
width  of  some  50 
feet.  No\\'  this  so- 
called  vein  proved 
to  be  a  decomposed 
dyke  of  porphyry 
impregnated  w  i  t  h 
pyrites  and  free  g')id, 
and  through  the 
dyke  ran  a  net-work 
of  little  narrow  quartz  veins  or  veinlets.  On  sampling, 
whilst  we  took  samples  clear  across  the  whole  width  of  the 
vein,  we  kept  those  fragments  which  came  from  the  quartz 
veinlets  apart   from  those  which  came  from  the  porphyry 

Surjcict  Drift     <0 


Plate  XCI. 

Natural  Appearance  of  Mine  on  a  Blanket  Ore 
Deposit. 


Plate  XCII. 

Geological  Section  Showing  Workings  and  Ore  Bodies  in  Contact  Blanket  Ore 
Body.     Shaded  Portions  are  All  Worked  Out. 

gangue.     The   result  was  vve   found  the  porphyry,  consti- 
tuting of  course  the  main  element,  to  be  barren  and  the 


i8i 

f^uld  to  be  concentrated  in  the  quartz  veinlets  constituting 
a  niininuun  of  the  width. 

So  in  a  vein  there  will  generally  be  parts  richer  than 
others,  "  pay  streaks"  as  they  are  called,  which  it  is  impor- 
tant to  distinguish,  also  certain  metallic  minerals  in  the 
vein  carrying  greater  values  than  others.  Thus  thejiyrites, 
if  undeconiposed,  may  prove  too  poor  to  treat  for  gold,  or 
in  a  silver  mine,  streaks  of  gray  copper  may  be  very  rich, 
whilst  bodies  of  coarse  galena  may  be  very  poor.  In  a  gold 
mine  it  is  important  for  the  engineer,  if  he  can,  to  find  out 
to  what  depth  surface  decomposition  or  oxidation  has  jiene- 
trated,  because  in  this  brown  rusty  matter  will  likely  be 
most  of  the  "  free  gold  ;  "  whilst  when  the  unoxidized  pyrites 
makes  its  appearance  the  ore  is  no  longer  free  ore,  but  must 
be  treated  by  some  process  other  than  that  of  a  stamp  mill, 


Pl.ATK   XCUI. 
I'lano-Scction  of  a  Flat  Ore  Body. 

and  with  the  incoming  of  pyrite  the  palmy  days  of  the  gold 
mine  may  be  at  an  end.  Sometimes,  however,  though  the 
oxidized  brown  gossan  may  play  out  and  succeed  to  white 
quartz,  the  latter,  if  it  be  not  too  hard,  white  and  "  hungry," 
may  still  continue  to  carry  free  gold  in  it.  Again  in  the 
veins,  with  their  descent  into  depths,  greater  or  less  rich- 
ness may  occur  or  different  varieties  of  ore  set  in,  or  abso- 
lutely barren  quartz,  so  if  there  be  shafts  or  tunnels  driven 
(jn  the  vein  a  distinction  should  be  noted  with  descent  as  to 
values  found  at  different  levels,  also  as  to  character  and 
richness  of  the  ore  above  and  below  water  line  ;  the  latter 
corresponds  to  the  average  drainage  level  of  the  country. 

This  completes   his    underground   examination.      Whilst 
in  the  mine  he  may  make  a  rough  sketch  or  two  of  the  vein 


ii 


■fi 


i8: 


:'-i  it 


::ni 


showing  the  general  disposition  of  the  ore  bodies  or  any 
pecuMarities.  (.)n  emerging  and  carefully  securing  his 
samples   beyond  reach   of  their  being   tampered   with,    he 

selects  a  convenient  point,  pos- 
sibly on  a  neighboring  hill  facing 
the  property,  and  takes  a  general 
sketch  of  the  property  in  pen- 
cil or  water-colors  (see  Plates 
LXXXIX,  XC,  XCl  and  XCII), 
also  makes  a  pencil  sketch  and 
ideal  section  of  the  hill,  showing 
the  position  of  the  vein  and  its 
workings  (see  Plates  XCV  and 
XC  VI),  the  amount  of  ore  stoped 
out  and  the  amount  presumably 

vrT-\;'  ^"  place  intact;  to  estimate  the 

PLATE  ACIV.  i^^jgj.  jg  yfj.^,j^  a  difficult  and  un- 

Expert  Taking  Samples.  certain  problem.     He  may  make 

some  sort  of  estimate  as  to  the  reasonableness  or  not  of 
the  price  asked  and  give  his  estimate  ;  he  can  form,  how- 
ever, no  true  estimate  of  the  value  of  the  ore  bodies  till  he 
has  had  time  to  assay  his  samples,  for  these  are  the  crucial 
test  of  the  value  of  the  propert)^ 


Plate  XCV. 

Fissure  Vein  Outcrop  on  Hillside  Showing  Surface  Workings. 

In  writing  up  his  report  at  his  leisure,  which  will  most 
likely  be  read  at  a  general  meeting  of  the  company,  he  can- 
not be  too  clear,  simple  and  explanatory  in  his  account  and 
its  details,  as  it  is  to  be  remembered  that  the  company  is 


'M' 


i83 


). 
id 


likely  larj^ely  to  be  composed  of  men  unacquainted  with 
mininf^  and  mininj^  terms ;  he  must  therefore  not  take  it  for 
granted  that  they  know  what  "stcjpes,"  "adits"  and  "jj^tMij^e," 
etc.,  are,  but  exjilain  as  he  jj^oes  alcMi^,  accompanyinja;^  his 
remarks  with  rouy^h  sketches  to  make  his  meaniiij^  clear 
and  put  the  members  of  the  company  as  much  on  tlie  j^round 
as  p(jssible.  We  ourselves  have  found  that  it  is  not  neces- 
sary, j^^eneraliy  to  make  elaborate  notes  in  the  field  or  U) 
write  pages  of  reading  matter  then,  provided  we  make  many 
sketches  and  on  them  put  down  items  such  as  length  of 
workings,  etc.,  etc.     The  sketch  is  generally  the  notes,  and 


funnel f  y 

Tunnel  Z   / 

^-.^ 

-*: 

^^ 

K:r-' 

r*- ^ 

Plate  XCVI. 

Cross  Section  of  Vein  Showing  Workings.     Dotted  Portion  is  Ore  Body,  Shaded  is 

Ore  Worked  Out. 

when  the  engineer  returns  home,  his  sketches  will  recall 
vividly  all  he  has  seen  and  from  these  he  will  write  his 
report.  Upon  certain  matters,  however,  such  as  involve 
numbers,  he  should  be  very  accurate  in  writing  notes  and 
not  trust  to  treacherous  memory  for  them. 

DESCRIPTION   0¥   PLATES. 

In  Plate  LXXXIX  we  have  an  actual  example  of  a  rather 
inaccessible  propert}-  in  the  San  Juan,  which  with  Plate  XC 
shows  the  kind  of  sketches  to  accompany  a  report.  In 
Plate  LXXXIX  with  its  section,  it  will  be  observed  how 
very  high  up  the  mining  holes  and  prospects  are  perched, 
in  most  cases  over  i,ooo  feet  above  the  valley,  and  again, 
before  the  ore  can  be  brought  over  to  the  mill,  a  ravine  of  a 
hundred  feet  deep  occupied  by  a  boiling  torrent  has  to  be 
crossed.     Some  of  the  properties  ni'ght  be  worked  perhaps 


r  \ 


I 


i84 


'•■  i 


M 


I 


i! 


by  a  suspension  tramway  thrown  acn^ss  the  f^iilch.  In 
another  case  a  trail  has  had  to  be  cut  in  loujr  z  gzaji^s  (jt 
some  miles  before  the  bott(jm  of  that  could  be  reached. 
Another  disadvantageous  feature  in  this  property  is  tiie 
number  of  scattered  veins,  none  of  them  very  rich  bv  itself  ; 
this  involves  a  separate  plant  or  workinj^s  for  each.     One 

food  vein  would  be  better  than  all  these  put  tofrether. 
here  is  fine  water  power  on  the  property  and  plenty  of 
timber. 

In  Plate  XC  there  is  one  fine  rich  g'old  vein  easily  accessi- 
ble and  easily  worked  ;  below  it  lies  a  natural  basin  and 
abundant  water  which  makes  it  an  adniirable  locatic^n  fur 
the  stamp  mill.  This  Plate  f^ives  an  idea  of  the  roujj^h  kind 
of  a  sketch  the  expert  makes  on  the  j^round,  which  he  em- 
bellishes and  elaborates  on  his  return. 

Plates  XCI,  XCII  and  XCIII  show  : 

(XCI.)  The  surface  appearance  of  a  "flat"  or  cc^ntact 
blanket  on  the  side  of  a  hill,  such  as  at  Leadville. 

(XCII.)  Cross-section  showing  the  position  f)f  ore  bodies, 
the  portions  worked  out  and  portions  probably  left  in  re- 
serve, also  the  workings  of  the  mine  and  the  geolcjgical  sec- 
tion, together  with  a  prominent  fault. 

(XCIII.)  Is  a  somewhat  ideal  sketch  oi  the  probable 
relations  of  a  flat  ore  bod}-  if  the  surface  matter  were  re- 
moved, or  rather  if  it  were  opened  like  a  book. 

Plate  XCIV  shows  the  expert  taking  samples  in  a  tunnel 
driven  in  the  vein  ;  the  vein  in  this  instance,  being  a  very 
large  one,  occupies  the  whole  width  of  the  tunnel;  this  is 
not  generally  the  case,  the  vein  and  ore  body  are  more  com- 
monl)'  observed  about  the  middle  of  the  roof,  /.  e.,  if  the  vein 
is  small. 

Plate  XCV  shows  the  outside  appearance  of  a  fissure  vein 
with  three  tunnels  down  in  it,  and  Plate  XCVI  shows  cross- 
section  and  profile  showing  the  tunnel  and  the  ore  bodies  s<j 
far  discovered  in  the  quartz  gangue  and  how  much  has  been 
worked  out. 


!!■!: 


1 85 


CHAPTER  XIV. 

SALTING   MIXES. 
In  these  clays  when,  owinj^  to  the  depression  ot  silver 


so 


much  attention  is  beinj^  turned  towardsjrold  and  fi^old  mines, 
too  much  care  cannot  be  tai<en  by  tliose  investing  or  act 
ing  as  examiners  or  experts  in  ^o\(\  mines,  that  there  are 
no  tricks  phiyed  upon  them  by  the  astute  miner;  for  "for 
ways  that  are  dark  and  tricks  tiiat  are  vain  "  the  western 
miner  is  at  times  "  pecuUar."  One  of  these  tricks  is  what  is 
known  as  "salting"  mines  or  ledges;  that  is,  by  \'arious 
means  and  ways  introducing  into  the  mine  or  into  the  sam- 
ples taken  from  it,  certain  rich  minerals  which  do  not  rightly 
belong  by  nature  in  the  mine  or  property,  in  order  to  raise 
the  value  of  the  mine  in  the  eyes  of  the  investcjr  or  expert. 
When  samples  are  taken  from  such  a  tampered-with  mine 
the  values  and  results  must  be  accepted  nn//  j^ra/io  sa/i's, 
with  a  very  large  grain  of  salt  indeed.  Whether  this  classic- 
al allusion  be  the  origin  of  the  word  "salting"  we  do  not 
know. 

"  Take  care  you  ain't  salted  "  is  the  advice  to  the  inexpe- 
rienced investor  or  novice  expert.  So  clever  are  the  miners, 
that  cases  are  on  record  where  even  a  most  experienced 
expert  has  been  taken  in,  and  comparatively,  or  wholly 
valueless  properties  sold  for  large  sums,  the  purchase  fol- 
lowed later  by  woeful  dismay  and  surprise,  Avhen  dividends 
were  called  for  and  did  not  appear. 

Gold  mines  of  all  others,  are  the  most  easy  to  salt,  hence 
the  precaution  in  these  davs  is  timely. 

Whilst  a  mining  engineer  or  expert  can  hardly  prevent 
salting,  with  care  he  can,  and  ought  to  be  able  to  avoid  being 
taken  in ;  to  be  forewarned  is  to  be  forearmed. 

On  entering  a  mining  camp  in  the  far  West,  especially 
in  the  more  remote  outlandish  districts,  an  investor  or  an  ex- 
pert, may  consider  that  the  whole  village,  from  the  ho  el 
bell-boy  to  the  mayor,  (who,  by  the  way  may  be  the  principal 
saloon  keeper)  is  in  league  against  him.  Directly  he  arrives, 
everybody  in  town  wants  to  know  his  business  ;  on  this  he 
should  keep  as  mum  as  possible,  and,  if  he  can,  throw  im- 
pertinent inquirers  off  the  scent.  The  idea  is,  "  Here  is  a 
capitalist  to  fleece  and  an  expert  to  delude."  E^'ery  one, 
too,  has  a  "  hole  in  the  ground  "  of  his  own  to  present. 
Should  they  get  wind  of  the    particular   property    in  view, 


i86 

there  are  confederates  and  middlemen  anxious  to  share  the 
spoils.  Moreover,  it  is  considered  to  thi'  jri-neral  crech't  of 
trie  camp  to  sell  a  mine,  be  it  whose  it  may,  ^oofl  or  bad.  and 
if  you  mention  any  property,  yon  will  invariably  hear  it 
"cracked  up."  Tlie  eastern  "  tenderfoot  "  is  somewhat  of 
a  "sheep  amonfj^  wolves  "  in  such  a  camp.  The  e.\pert,  too, 
i.s  at  a  certain  disarivanta^^e  on  enterinjj^  into  a  stranjj^e  min- 
iiiff  catnp,  not  bein^'-  familiar  with  the  local  conditions.  Ores 
for  instance  in  (Mie  section  or  rejj^ion  are  not  always  of  the 
same  value  as  similar  ores  in  another,  the  rocks  may  look 
new  and  stranj^e  to  him,  and  there  are  a  hundred  local  coufli- 
tions  known  only  to  the  resident  miner.  It  would  be  well, 
when  p(;.-isible,  for  an  expert,  before  passin/^  a  decided 
opinion  on  an  important  pujperty,  to  stay  around  in  the 
vicinity  for  a  whde  till  he  kn<nvs  the  "  hanji^of  things." 

On  Ills  way  tothe  mine  there  will  be  plenty  to  fill  his  ears 
with  the  untold  value  of  the  property  he  is  about  to  examine, 
this  friendly  duty  is  not  unfre(|uently  performed  by  an 
ollicicnis  middleman.  To  favor  and  "soften  up"  the  ex- 
l^ert's  mind  and  heart  and  make  him"  feel  ^ood"  toward 
the  propertv,  attentions  of  all  kinds  are  showered  on  him. 
He  is  driven  about  town  like  a  nabob,  and  if  he  shows  a 
weakness  for  a  "  wee  drappie,"  champaja^ne  and  whiskey  are 
at  his  service  ad  lib.,  as  judicious  preparation  for  thecominjj;' 
examination.  It  may  be  observed  here,  that  attempts  are 
made  sometimes  to  "  salt  "  the  expert  as  well  as  the  mine, 
not  merely  \i\  befuddlinji;^  his  brain  with  intoxicants,  but  by 
olferin.a:  bribes,  and  as  an  expert  is  often  not  too  well  off, 
the  latter  is  a  jj^rea.,  temptation. 

We  will  now  suppose,  after  this  ordeal,  he  ja^oes  to  the 
mine  with  the  superintendent  or  miner.  All  may  be,  and 
we  may  say  generally  is,  honest  and  square,  or  it  vuxy  not. 
The  expert  looks  over  the  exterior  and  surface  signs  of  the 
property,  studies  the  outcrop  of  the  vein  on  the  surface,  its 
probable  surface  continuity,  the  adv^antages  and  disadvant- 
ages of  the  situation  of  the  mine,  its  proximity  to  railroads, 
smelting  works,  markets,  etc.,  and  then  enters  the  mine  in 
company  with  the  miner.  As  a  rule  the  latter  will  natur- 
ally point  out  to  him  the  richest  portions  and  ignore  the 
poorer;  sometimes  he  excuses  himself  from  taking  him 
down  into  the  latter  because  it  is  dangerous  or  full  of  water. 
If  full  of  water  the  expert  if  possible  should  have  it  pumped 
out.  He  may  sup^gest  here  and  there,  that  such  and  such  a 
spot  would  be  a  good  one  for  the  expert  to  take  his  samples 
and  so  forth.     The  expert  of  course  assents  to  all  he  is  told, 


i87 


but  with  Diic  eve  open,  and  does  not  stop  to  take  any 
samples  for  assaying  until  he  has  seen  the  whole  of  the 
mine,  then  he  refiuests  his  companion  to  f^o  ,,iit  on  the 
dump  and  smoke  his  pine  there,  as  he  insists  upon  ha\injjf 
no  one  with  Idm  in  tiie  tunnel  when  he  is  takinjj;  his 
samples  for  assay.  He  will  he  inclined  to  rather  avoid 
those  particularly  favorable  spots  sufi:gested  to  him  by  the 
miner,  as  probably  jj^ivinjj^  to(>  rich  an  average  for  the  general 
1  un  of  the  mine,  or  as  not  imjiossibly  being  "  fixed  "  for  him. 
If  he  suspects  the  latter,  he  will  take  a  sample  or  two  to  see 
if  the  mine  has  been  tampeied  with,  taking  a  little  oi  this 
out  on  the  dump  crushing  it  and  washing  it  in  an  iron 
spoon.  If  a  very  astonishing  amount  of  gold  c(dors  show 
up,  his  suspicions  arc  aroused.  The  judicious  miner  does 
not  generally  want  to  salt  too  heavily,  for  fear  of  the 
enormous  results  exciting  suspicion,  but  despite  his  care  he 
nearly  always  salts  a  little  higher  than  he  intended.  In  a 
mine  where  the  rock  is  hard,  a  miner  may  salt  by  drilling 
holes  and  inserting  mineral  or  ore  and  disguising  the  hole. 
In  loose  ground  or  one  full  of  cracks,  a  shot-gun  loaded 
with  a  moderate  discharge  of  gold-dust  will  do  the  work. 
The  skill  of  the  miner  in  this  case  lies  in  his  choice  of  a  spot 
where  he  thinks  it  probable  the  expert  will  take  samples,  ov 
in  coaxing  the  expert  to  take  samples  from  such  ground. 
In  hard  ground  the  expert  may  avoid  such  salting  by  having 
the  work  blasted  out  in  his  presence  till  a  purely  fresh, 
\'irgin  face  is  shown  and  then  taking  his  sample.  These 
precautions  are  not  necessary  under  all  circumstances,  but 
only  in  such  cases  where  the  expert  has  a  suspicion  that 
there  is  an  attempt  to  "  put  up  a  job  "  on  him. 

After  getting  nis  samples,  and  as  many  as  possible,  he 
will  sack  and  seal  them  then  and  there  in  the  mine,  and 
never  lose  sight  of  them  till  he  has  expressed  them  to  his 
own  home. 

Sometimes  a  mine  is  so  timbered  up,  that  sampling  is 
ditRcult.  Now  as  they  go  down  the  shaft,  it  may  be  the 
expert  remarks  "  I  should  like  to  take  a  sample  in  this  shaft, 
but  it  is  so  timbered  up  that  I  don't  see  how  we  can  do  it 
without  ripping  out  some  of  these  boards."  "  Why  of 
course,  so  you  oughtter  "  says  the  miner,  "and  see  here,  I 
think  this  board  is  loose."  Now  beware  lest  that  board  was 
purposely  loosened  and  behind  it  the  ground  is  salted. 

By  taking  a  great  number  of  samples  at  comparativel)'  close 
intervals,  provided  afterwards  the  samples  are  not  tampered 
with,  the  expert  is  less  liable  to  be  deceived  by  salting,  than 


V^ 


if 


17 


f! 


if  he  took  \er)-  frw.  A  mine  cannot  be  salterl  all  over  fvom 
eiul  to  end  if  it  is  a  larjj^e  one,  only  at  judicions  inter\-als, 
and  it  will  be  bard  if  tbe  expert  does  not  escape  some  of 
tbose  interx'als  aiul  >j;et  some  true  sampli's. 

Besides  taking  bis  rej^ular  assay  samples  by  ciittinjj;  all 
around  tb.;  wal's,  roof  and  lloor  of  tbe  tunnels  at  intervals 
of  five,  ten,  or  twenty  feet,  accordinj^  to  circumstances, 
crusliinjr,  and  quarterinjj;  tbe  debris,  aufi  finally  sackinjj^  and 
sealiiif^  bis  sampli'  bajj^s,  be  sbould  occasionally  take  a  "j^rab 
sample,"  or  a  bit  of  rock  at  random,  or  a  small  sackful 
from  tbe  jj^reat  mass  of  bis  sample,  and  put  tbem  in  bis  coat 
j)ocket,  and  keep  tbem  on  bis  person,  to  act  as  a  reference 
in  case  of  any  possible  tampering  or  accident  to  bis  samples 
wbilst  in  tbe  vicinity  or  in  transit.  He  sbould  also  take 
bulk  samples,  ^ood  sixcd  cbunks  of  uncrusbed  rock  wbicb 
sbould  ajj^ree  with  tbe  assay  results  of  bis  quartered  samples. 

A  disadvantage  an  expert  is  under  in  a  strange  camp,  if 
he  cannot  take  bis  own  assistant  with  him,  is,  that  he  is 
very  much  at  the  mercy  of  the  miner,  if  any  hard  work  has 
to  be  d(Mie,  such  as  blasting  or  bard  fligging.  Whilst 
engaged  in  such  work  tbe  miner,  if  be  ple.ises,  has  man\' 
chances  of  scattering  around  a  little  gold-dust  on  the  rock 
of  tbe  vein  or  tiie  loose  dirt  of  a  placer. 

Whilst  gold-dust  is  the  favc^rite  medium  for  salting  a  gold 
mine,  chloride  of  gold  is  sometimes  used.  The  latter,  how- 
ever, is  rather  a  dangerous  and  barefaced  trick  to  try  on 
a  competent  expert,  as  its  qualit)'  can  readil\'  be  detected 
by  the  chemist,  it  being  scdubic  in  water.  In  a  case  of  this 
kind  that  came  to  our  knowledge,  an  expi'rienced  expert 
liad  examined  a  certain  mine  and  condemned  it.  Later,  the 
owner  who  was  an  honorable  man,  asked  him  if,  as  a  special 
favor,  be  would  re-examine  it,  as  in  bis  absence  tbe  assa\' 
values  fnjm  the  mine  had  of  late  shown  much  better  results. 
The  expert  reluctantly  consented  to  do  this,  though  con- 
trary to  his  general  rule.  In  going  along  tbe  workings  be 
noticed  here  and  there  on  the  walls,  certain  patches  and 
streaks  of  clay  or  mud,  be  had  not  t)bserved  on  his  first 
visit.  Guessing  what  they  were,  he  casually  observed  to  tbe 
miners,  "Seems  to  have  been  raining  in  tbe  mine  since  I 
was  here."  However  to  the  great  delight  doubtless  of  the 
miners  be  took  several  samples  of  these,  and  forwarded 
tbem  to  a  reliable  chemist.  The  latter  pronounced  tbem 
chloride  of  gold.  This  of  course  gave  tbe  salting  scheme 
away  as  chloride  of  gold  does  not  occur  free  in  nature,  much 
less  in  a   mine.     Tbe  owner  of  the  mine  was  exceedinglv 


I. Si 


:inj4:rv  wlicii   lit-   Icarncfl  wliat   the   miiu.Ts  had  done  williotit 
his   knowlcflj^'o  or  coiiiiivaiiCL'.     'I'lic  im-ii  tlioiiiscKcs  l)ciiij^' 


coininoii 


ly 


niori;  or  less  iiitort-sU-fl  m  the  sale  ot  a  lume,  arc 


apt  to  try  and  sah  it  without  any  <'oniiivaiiCt'  ol  t hi"  owner 
or  siipfriiitciidiMit.  We  hi'ard  ot  a  case  in  the  San  |uan 
rUstrict  where  a  mine  tliat  was  fairly  jrood  was  about  to  l)e 
examined.  This  mine  canied  occasionally  s|)f(iinens  of  the 
\ery  rich  ore,  called  ruhy  silver.  Not  satisfied  with  the  lair, 
natural  richness  of  the  mine,  the  miners  must  nei;fis  import 
into  tile  hole,  (|uantities  of  ruhv  coJU'cted  from  other  mines 
in  the  flistricf,  whose  men  were  of  coiirsi;  in  svmpathv  with 
the  scheme  and  probabk-  sale.  This  was  acting'  without  the 
knowledjj^e  of  the  owners. 


SAI.I'INC.    (lOI.D    iM.ACKKS. 

.\ltlioiif.(li  a  fj^ojd  placer  usuall)' coxcrs  a  \ery  h\\^;c  area 
of  jjfroiiiul,  it  is  possible  to  salt  it.  Usually  a  miner  shows 
up  ills  placer  by  openinjic  up  [lits  at  convenienf  intervals,  so 
as  to  cover  the  jiroperty.  Xothinjj;  is  easier  than  to  salt 
these  pits  with  jj^olrl-rlust.  ("oiise(pit'iitly  whilst  an  expert 
wii!  examine  these  holes  and  |)an  the  flirt,  he  should  be  on 
his  jj^uard,  and  insist,  where  possible,  on  holes  beiiifj^  freshly 
duj,,'  in  his  presence.  Kvcn  then  he  is  not  safe,  (ienerally 
in  a  placer,  by  the  cuttinj^  of  a  stream,  sections  are  shown 
sometimes  from  j^^rass  roots  to  befl  rock.  From  such  he 
shcjuld  take  and  pan  samples  at  dilTerent  le\els  in  the 
exposure,  this  too,  prixatelv  and  without  too  much  sujier- 
\ision  (jf  the  interested  miner. 


SAI/I'INC.    ASSAN'    SAMI'i.KS. 

This  may  be  done  in  several  ways.  If  the  expert  is  im- 
prudent enou<j;h  to  allow  a  miner  to  accompany  and  assist 
lim  in  breakinj^  down  or  crushiii,i»^  samples  or  panninj,^  them, 
then  the  infusion  of  a  little  fi;old-dust  is  easy.  A^aiii,  after 
the  expert  has  made  up,  sacked  and  duly  sealed  his  samples 
with  wax,  should  he  leave  them  anywhere  within  reach  of 
the  miners,  they  are  not  wholly  saft',  for  the  miner  may  in- 
sert the  point  of  a  tine  svriiifi^e  containiiifj;  jj^old-dust  into  the 
baj2f.  or  he  mav  make  a  bread  mould  of  the  wax  seal,  open 
the  sacks,  and  either  change  the  ore  for  richer,  or  infuse 
some  fi^old-dust.  Chaii<>-inj4-  of  samples  for  others  is  not  an 
unccMnmon  trick.  The  expert  cannot  watch  his  samples  too 
cl<:)sely.     lie  shou'''  sack  and  seal  them  on  the  gr(  and,  sleep 


ipo 


with  them  under  his  pillow  if  need  be  at  nij:(ht,yet  even  then 
cases  have  been  known  when  the  wary  miner  has  succeeded 
in  extracting  and  changing  them  for  bags,  to  all  appearance 
exactly  similar.  The  samples  are  never  safe  till  boxed  up 
and  expressed  and  on  the  way  to  the  city  address.  He 
should  never  fail,  as  we  have  said,  to  have  partial  duplicates 
of  these  about  his  person. 

If  the  expert  wishes  to  assav  the  ore  at  a  friendly  assay 
office  near  the  mine,  whilst  ho  is  grinding  down  his  sample 
to  dust,  an  innocent  looking  miner  may  loaf  in,  and  wliMst 
watching  the  operation,  accidently  upset  the  ashes  in  his 
pipe  over  the  sample.  Probably  these  ashes  contain  gold- 
dust,  and  we  might  here  observe  that  a  single  grain  of  gold 
smaller  than  a  pin's  head  may  materially  alter  the  results  of 
an  assay. 

Some'  years  ago  an  individual  who  had  succeeded  in 
booming  a  certain  placer  distiict  and  getting  up  an  excitement 
and  a  rush,  constituted  himielf  as  a  referee,  and  professor  ; 
and  when  miners  brought  samples  for  his  inspection,  the 
were  always  found  to  be  very  rich  in  gold.  But  simila 
samples  from  the  same  spot  if  uninspected  were  somehow 
invariably  barren.  The  wizard's  mere  look  seemed  to  change 
the  sand  into  gold,  until  it  was  found  that  he  concealed  in 
his  finger  nails  "which  wei"e  taper"  not  wax,  but  fine  par- 
ticles of  gold.  Hence  Midas-like  whatever  he  touched  he 
turned  into  gold.  Whilst  the  salter  may  lay  traps  for  the 
expert,  the  expert  may  sometimes  lay  traps  for  the  Salter. 
An  expert,  who  had  reasons  to  suspect  a  certain  mine  he 
was  examining  had  been  tampered  with  and  guessing  there 
was  a  likelihood  of  an  attempt  on  his  samples,  after  securing 
himself  with  duplicates,  left  his  samples  exposed  on  the 
floor  of  his  room  :  t  the  hotel,  then  went  out  and  hired  a 
reliable  Mexican  boy  to  watch  his  room  and  report  to  him 
immediately  if  he  saw  any  one  enter  it.  He  had  not  long  to 
wait.  At  dinner  the  boy  tapped  him  on  the  shoulder,  and 
he  went  to  his  room  and  caught  the  miner  in  the  act  of 
tampering  with  his  samples. 

Sometimes  miners,  if  wealthy  enough,  will  go  to  great 
expense  to  salt  a  property.  Some  miners  took  a  couple  of 
Avell-to-do  eastern  capitalists  to  a  certain  placer,  panned  the 
gravel  before  their  eyes,  and  showed  up  wondrous  colors. 
The  investors  having  been  warned  of  miners'  ways,  refused 
to  entirely  swallow  the  bait,  but  told  the  boys  to  go  ahead 
and  develop  the  property,  and  if  at  their  next  visit,  it  show- 
ed up  as  well  as  the  pans  did  on  this  occasion,  they  would 


191 

buy  it.  When  the  easterners  were  j^^one,  at  a  cost,  of  several 
tliousand  dollars  they  built  a  tlunie,  put  in  a  hydraulic 
pla'U,  and  g-athered  a  pile  of  loose  dirt  to  wash  down  the 
flume,  where  the  f^o!d  is  feathered  upon  cjuicksilver.  Tlie 
"  sharks  "  raised  $50,000  for  a  gold-dust  fund.  This  dust  was 
run  evenly  over  the  quicksilver  so  that  when  the  capitalists 
returned,  there  was  everything  to  show  an  enormously 
rich  placer-ground.  The  capitalists  insisted  upon  aclean-uj) 
after  the  first  fortnight's  run,  which  added  so  much  more 
joy  to  the  sharks.  This  time  the  bait  was  swallowed  whole, 
string  and  all.  The  capitalists  paid  down  promptly  $250,000 
for  the  ground.  The  sharks  left  the  country.  In  a  feu- 
weeks  nothing  could  be  found  but  the  amalgam  of  the 
sharks. 

An  ingenicjus  trick  once  baffled  some  experienced  ex- 
perts and  came  ver}-^  near  selling  a  mine.  The  mine  was  a 
well  developed  one  and  had  done  great  things  in  its  day. 
It  was  claimed  that  at  the  face  of  the  tunnel,  or  where  the 
workings  left  ofT,  there  was  still  a  fine  showing  of  ore  in 
place  to  go  on  with.  The  experts  found  it  as  stated;  on  the 
face  or  end  of  the  tunnel  there  was  a  fine  showing  of  ore, 
and  the  probable  amount  in  place  and  for  the  future  was 
duly  measured  up  and  estimated.  It  leaked  out  later  that 
this  block  of  ore  was  only  a  thin  screen  purposely  left,  all 
back  of,  and  behind  it,  having  been  carefully  worked  out 
and  the  opening  foi  the  miners  ingress  and  egress  skilfully 
concealed.  The  mine  was  re-examined,  the  cheat  discovered 
and  the  reputation  of  the  experts  saved  as  well  as  many 
thousands  of  dollars  from  the  pockets  of  guileless  investors. 

This  brief  sketch  of  some  of  the  ways  of  some  miners,  for 
some  regions  and  properties,  would  give  an  unfair  idea  of 
some  mines  and  miners  as  a  whole,  if  it  were  supposed  that 
all  miners  are  given  to  salting,  and  all  properties  for  sale  are 
beset  by  a  network  of  dishonest  devices.  On  the  contrary 
manv,  vtry  many,  miners  are  as  straight  as  a  string  and 
hundreds  of  properties  are  to  be  examined  without  fear  of 
tampering.  But  it  often  happens  that  a  miner,  who  in  every 
other  relation  of  life,  is  as  honest  as  the  da\',  diaws  a  line, 
when  it  comes  to  the  selling  of  a  mine,  which  he  considers 
"  fair  game." 

But,  as  elsewhere  the  world  through,  honesty  pure  and 
simple  is  the  right  policy,  and  in  the  end  would  be  found 
the  best  paying  one.  For  the  notorious  dishonesty  con- 
nected with  mines  (much  more  common  in  the  past  than  in 
the  present)  scares  away  capitalists  from  investing,  whilst 


Jii 


I 


192 

if  truth  and  honesty  were  maintained,  money  would  roll  in 
freely. 

One  lesson  at  least  may  be  learned  from  what  we  have 
said,  and  that  is,  that  if  in  some  cases  a  professional  expert 
is  ever  taken  in,  what  chances  has  a  capitalist,  ignorant  of 
mines,  to  buy  a  mine  on  his  own  examination?  What  man 
ignorant  of  horseflesh  would  venture  to  buy  a  steed  from  a 
professional  horse-jockey,  without  taking  with  him  a  friend 
who  is  knowing  about  horses  ? 

How  much  more  so  in  such  a  difficult  and  delicate  problem 
as  that  of  purchasing  a  -mine,  is  it  the  duty  of  an  investor 
never  to  purchase  or  induce  his  friends  to  purchase  a  mine, 
until  he  has  employed  the  services  of  a  competent  expert  to 
previously  examine  it.  If  the  expert's  fee  should  amount  to 
a  few  hundreds,  and  after  all  he  should  decide  on  condemn- 
ing the  property,  it  is  far  better  for  the  company  to  entail 
this  expense,  and  perhaps  lose  this  small  sum,  than  to 
involve  themselves  in  the  loss  of  thousands  of  their  own  as 
well  as  other  people's  money  in  a  bogus,  w^orthless,  or  wild- 
cat scheme. 


CHAPTER  XV. 


PROSPECTORS'    TOOLS    AND    HOW   TO    SHARPEN    AND 

TEMPER    THEM. 

The  principal  tools  a  prospector  take.,  into  the  field,  are 
picks,  drills,  hammers  and  shovel. 

A  prospector,  esp^-cially  when  climbing  mountains,  likes 
to  be  as  light-handed  and  unencumbered  as  possible. 

For  his  trip  as  a  whole,  i?e  may  carry  several  different 
tools  packed  on  his  donkey,  but  when  he  has  arrived  at  a 
locality,  the  vicinity  of  which  looks  likely,  he  leaves  most  of 
his  heavier  tools  in  his  temporary  camp,  or  near  to  where 
he  pickets  his  pack  animal.  He  makes  a  short  excursion  up 
the  mountain  for  a  general  reconnoitre,  armed  with  nothing 
more  than  a  light  prospecting  pick,  weighing  not  more  than 
three  or  four  pounds.  This  little  pick  is  about  ten  inches  in 
length, with  a  handle  about  fifteen  inches  long;  the  longer 
portion  is  sharpened  into  a  pick,  and  the  shorter  ends  in  a 
square  faced  hammer.  We  recommend  a  square  sharp 
cornered  face  to  the  hammer,  in  preference  to  the  bevelled 


ii 


•93 


111 

•e 

rt 


a 

id 

in 


face,  as  the  sharp  edges  and  corners  are  better  adapted  for 
breaking  rock  than  the  rounded  or  bevelled  ends.  This 
prospecting  pick  or  geological  pick  and  hammer,  should  be 
all  of  good  steel,  with  a  good  sized  eye  to  admit  a  springy 
handle  of  hickory.     See  Plate  XCVII,  Figs,  i,  i,  i. 

0  ,  Armed  with  this  little  weapon 

he  climbs  the  hillside,  hunting 
for  "  float  "  oi  for  rusty  outcrops, 
of  ledges.  Loose  pieces  of  rock 
he  cracks  open  with  the  hammer 
end,  softer  rock  in  place  he 
explores  with  the  pick.  "  When 
I  am  climbing  over  the  hills," 
said  an  old  weather-beaten  pros- 
pector to  me,  "  I  want  nothing 
but  my  little  pick,  then  if  1  find 
anything  likely  '  in  place,'  I 
mark  the  spot,  and  go  on,  and 
at  noon  I  come  d(  vn  to  camp, 
or  to  where  the  '  burro  '  is  feed- 
ing, I  take  up  my  heavy  digging 
pick  and  shovel  and  '  open  up  '  ; 
this  will  occupy  'ne  till  evening 
at  least,  then  if  I  find  there  is  a 
ledge  worth  more  thorough  ex- 
ploring, I  leave  my  tools  by  the 
hole,  and    next   morning   bring 

up  the  drills,  hammers  and  blasting  outfit.  But  the  first 
thing  1  would  advise  a  tenderfoot,  is  to  ge^  /i/s  eye  iraincd, 
trained  to  looking  for  float  and  observing  mineral  signs, 
trained  to  the  whole  business  of  close  observation.     Why  I 

1  myself,  old  hand  as  I  am,  after  being  awaj^  for  some 
months  about  town  or  looking  at  other  things,  can't  get  my 
ey^  in  and  down  to  it  for  two  or  three  days  ;  then  it  kind  of 
comes  natural. 

"  You  must  have  an  eye  for  float  and  rocks  like  an  artist 
has  an  eye  for  color,  and  a  musician,  an  ear  for  music.  A 
tenderfoot  had  better  go  along  with  an  old  hand  for  a  few 
daj'^s  to  get  into  training." 


Rbcks   and  Hammers. 

Plate   XCVII. 


11^ 


DESCRIPTION   OF   TOOLS,    PICKS   AND   DRILLS. 

Picks  and  drills  are  the  main  tools  that  need  sharpening 
and  tempering.  The  kind  of  sharpening  and  .lature  or 
degree  of  tempering  depend  upon  ♦^^he  kind  of  work  or  kind 


'. 


m 

of  rock  to  be  worked,  whether  hard  or  soft,  loose  grained 
or  fine  grained,  siHceous  or  clayey.  Drills,  for  example, 
would  have  to  be  differently  sharpened  and  tempered  for 
hard  vitreous  quartzite  than  for  soft  sandstone  or  hardened 
clay.  The  same  remark  applies  also  to  picks.  Picks  may 
be  double  pointed  or  single,  or  with  a  hammer  head  called  a 
poll,  it  it  is  to  be  used  for  breaking  rock.  The  main  points 
oft  a  pick  are,  strong  cutting  tips,  stout  eye  and  a  tight 
handle.  The  little  prospecting  pick  is  made  of  the  best  steel 
throughout,  but  in  the  heavier  pick,  the  wearing  parts  are 
the  tips,  which  should  be  replaceable.  An  all  steel  pick  is 
liible  soon  to  be  shortened  up  and  useless,  whilst  tlie  iron 
pick  eye,  a  14  inch  length  of  best  iron,  gives  long  service  by 
welding  on  tip  ends,  whenever  desired.  Professor  Ihlseng, 
in  his  "Manual  of  Mining,"  as  also  Mr.  George  Andre, in  his 
book  on  "  Rock  Blasting,"  give  excellent  descriptions  of 
tools  used  as  well  as  the  mode  of  sharpening  and  tempering 
them ;  to  them  we  are  indebted  for  many  of  the  details  of 
this  article,  and  to  their  works  we  refer  the  reader  for 
further  information  on  this  subject.  "  The  picks  are 
sharpened  to  form  on  an  anvil,  and  commonly  drawn  to  a 
four  sided  pyramidal  point,  for  hard  rock,  and  a  slim  taper 
for  fissured  rock,  and  a  bluff  taper  to  cut  crisp  ground,  and 
to  a  chisel  end  for  chipping  the  ground.  The  eye  is  oval 
and  well  surrounded  with  metal.  All  the  strain  of  the  pry- 
ing falls  on  the  eye,  which  must  be  true  and  stout." 


DRILLS. 

"  The  drill  is  a  bar  which  has  one  cutter  edge  and  one 
hammer  end.  It  iS'of  round  or  octagonal  steel.  Drills  may 
be  of  various  lengths,  from  a  foot  to  four  or  five  or  even 
more  feet.  For  prospecting  purposes  two  or  three  medium 
short  drills  from  two  to  four  feet  are  generally  enough,  as 
the  prospector's  business  is  rather  to  find  than  to  develop. 
In  beginning  to  drill,  it  is  common  to  use  a  short  thick  drill, 
with  a  stout  'bull  edge'  rather  than  a  thin,  tapering  one, 
especially  in  hard  rock ;  smaller  sized,  /.  e.,  narrower  drills 
may  be  used  for  increasing  depth. 

"  The  rock  drill  consists  of  chisel  edge,  bit,  stock  and 
striking  face.  To  allow  the  tool  to  free  itself  readily  in  the 
bore  hole,  and  to  avoid  introducing  unnecessary  weight 
onto  the  stock,  the  bit  is  made  wider  than  the  latter.  In 
hard  rock,  the  liability  of  the  edge  to  fracture  increases  as 
the  difference  of  width  ;  the  edge  of  the  drill  may  be  straight 


195 


'  !  I 


or  slightl}'  curved,  a  straight  edge  cuts  more  freely  than  the 
curved  ;  a  bull  bit  for  i^ard  rock  isgenerally  curved,  a  straight 
edge  is  vveaKer  at  the  corners  than  the  curved.  The  width 
of  bits  varies  from  i  inch  to  2^'  inches.  Figs.  1,2,  la,  2b,  Plate 
XCVIII.,show  the  straight  and  curved  bits  and  angles  of  cut- 
ting edges  for  use  in  rock.  The  stock  is  octagonal  in  sec- 
tion. It  is  made  iri  lengths  varjdng  from  20  inches  to  42 
inches.  The  shorter  the  stock,  the  more  effectively  it  trans- 
mits the  force  of  the  blow.  To  insure  the  longer  drills 
working  freely  in  the  hole,  the  width  of  the  bit  should  be 
very  slightly  reduced  in  each  length.  Diameter  of  stock  is 
less  than  the  width  of  the  bit  generally  by  y%  of  an  inch, 

"  The  smith  cuts  up  the  '  borer '  steel  bars  into  desired 
lengths  to  form  the  bit,  the  end  of  the  bar  is  heated  and 
flattened  out  by  hammering  to  a  width  a  little  greater  than 
the  diameter  of  the  hole  to  be  bored.  The  cutting  edge  is 
then    hammered   up  with  a  light  hammer  to  the  requisite 

1  2  IH^,4. 


i3 


T?      f//      O 


:ia 


Drill  In  hole 
in  rock. 


Tt4m  COLLttHY  CNnrntE^ 


;i  h 


rtr 


Plate  XCVIII. 

Forms   of  Drills. 

angle  and  corners  beaten  in  to  give  the  exact  diameter  of  the 
bore  hole  intended.  The  drills  are  made  in  sets  and  the 
longer  stocks  will  have  a  bit  slightly  narrower  than  the 
shorter  cies  for  reasons  already  given.  The  edge  is  touched 
up  with  a  file.  Heavy  hammering  and  high  heats  should  be 
avoided.  The  steel  should  be  v/ell  covered  with  coal,  in 
making  the  heat,  and  protected  from  the  raw  air.  Over- 
heated or  burned  steel  is  liable  to  fly,  and  drills  so  injured 
are  useless  until  the  burned  portion  has  been  cut  away. 
Care  is  required  to  form  the  cutting  edge  evenly,  and  of  the 


n 


196 

full  f<Mni.  If  the  corners  get  hamnicred  as  in  Fig.  3(?,  Plate 
XCVIII.,  they  are  said  to  be  'nipped  '  and  the  tool  will  not  free 
itself  in  cutting.  When  a  depression  of  the  straight  in- 
curved line  forming  the  edge  occurs,  as  Fig.  3/;,  the  bit  is  said 
to  be  'backward  '  and  when  one  of  the  corners  is  too  f:ir 
back,  as  Fig.  3^,  it  is  spoken  of  as  'odd  cornered.'  Either 
of  these  defects  causes  the  force  of  the  blow  to  be  thrown 
upon  a  portion  only  of  the  edge,  which  is  thereby  over- 
strained and  liable  to  fracture," 

SHARPENING     TOOLS. 

Professor  Ihlseng  in  his  "  Manual  of  Mining"  says  :  "  The 
best  fuel  for  blacksniithing  may  be  a  slightly  caking  coal, 
giving  fianie  and  high  heat.  Coke  is  hotter  but  harder  to 
keep  fire  in.  The.  fuel  should  be  as  free  from  sulphur  as  pos- 
sible. White  ash  coal  is  better  thxn  red  ash  ;  sulphur  makes 
the  iron  hot  short,  and  tends  to  produce  scales.  The  coal 
should  be  clear  of  shale  or  slate,  for  the)-  fuse  and  make  a 
pasty  cinder  that  is  annoying." 

A  prospector  away  from  civilization  may  have  to  use  wood  ; 
in  that  case  he  should  use  chips,  and -blow  them  with  a  port- 
able bellows. 

The  prospectors  who  try  to  get  ahnig  on  as  small  an  out- 
fit as  possible  usually  take  one  to  three  blasting  powder 
cans  and  cut  the  heads  out  of  all  but  the  bottom  one,  and  one 
head  of  that  must  be  cut  out ;  these  they  place  one  on  top  of 
the  other  to  make  a  furnace.  They  punch  an  inch  and  a  half 
hole  in  the  side  of  the  bottom  one  at  the  bottom  for  draft 
and  to  put  in  the  points  of  the  tools  to  heat  them. 

They  use  charcoal  for  fuel  and  then  a  chunk  of  steel  or 
railroad  iron  about  6  inches  long  serves  for  an  anvil.  Some 
take  a  small  bellows  and  anvil  with  them.  For  tempering 
drills  they  give  the  drill,  when  red,  a  plunge  in  water.  After 
two  or  three  rubs  on  wood,  to  brighten  it,  they  hold  it  up  to 
the  light  and  watch  it  until  it  takes  on  a  straw  color.  Then 
they  dip  it  in  water  again.  For  picks  a  blue  color  is  the 
most  satisfactory  in  general. 

"  Steel  is  a  compound  of  iron  and  carbon  and  its  homo- 
geneity and  presence  of  carbon  imparts  to  it  a  capability  of 
hardening  and  tempering  to  a  degree  depending  on  the  tem- 
perature of  the  heating  and  subsequent  cooling.  As  the 
amount  of  carbon  increases,  the  melting  point  of  the  iron 
decreases,  and  this  greater  fusibility  reduces  its  welding 
quality. 


'97 

"  A  steel  is  called  '  hardened  '  when  it  has  been  suddenly 
cooled  and  thereby  become  as  hard  as  possible.  This  is 
owing  to  the  presence  of  carbon,  for  pure  malleable  iron  is 
not  affected  by  the  operation,  while  both  steel  and  cast  iron 
are  to  a  marked  degree. 

"  The  operation  consists  in  forging  the  steel  to  a  certain 
degree  of  temperature,  and  then  plunging  it  into  some  fluid 
which  abstracts  the  heat  from  the  tool.  The  quicker  it  is 
done,  and  the  greater  the  difference  of  temperature,  the 
harder  is  the  to(jl.  Either  water  or  oil  is  used  ;  both  volatilize 
at  a  temperature  much  below  that  of  the  immersed  tools,  so 
the  hardening  takes  place  in  a  vapor;  oil  generally  produces 
the  best  effects.  On  the  first  plunge  the  metal  is  chilled 
and  coated  with  soot,  after  which,  a  slow  process  of  cooling 
takes  place." 

TEMPERING. 

"  Tempering  follows  hardening,  whereby  the  steel  is  sub- 
jected to  a  subsequent  lower  heat,  which  softens  it,  and 
removes  its  brittleness.  When  the  hardened  iron  is  slowly 
reheated,  its  surface  gradually  assumes  phases  of  color,  begin- 
ning .v'ith  a  light  straw,  passing  through  shades  of  yellow, 
brown,  purple,  blue  and  red.  At  a  cherry-red  heat,  the 
original  color  before  hardening,  the  effects  of  the  chilling  are 
practically  removed. 

"  Tempering  consists  in  carrying  the  second  heat  to  one  of 
the  above  mentioned  colors,  according  to  the  amount  of  the 
brittleness  to  be  annealed.  This  depends  upon  the  use  to 
which  the  article  is  to  be  put.  A  second  stage  of  the  opera- 
tion finishes  the  job.  The  aforementioned  reheat,  goes  on  a 
little  way  beyond  the  desired  color.  The  tool  is  carefulh^ 
plunged  part  way  into  the  water  or  oil,  till  the  disappearance 
of  the  steam  indicates  that  it  is  cold,  when  another  portion  of 
the  distance  is  further  immersed  for  a  moment.  The  tool  is 
withdrawn,  the  scales  rubbed  off  and  the  heat  of  the  remain- 
ing portion  draws  to  the  edge,  until  it  has  assumed  the  proper 
tempering  color.  It  is  then  thoroughly  cooled.  The  idea 
that  the  steel  is  cooler  at  a  blue,  than  at  a  yellow,  in  final 
drawing,  is  erroneous ;  for  more  of  the  heat  is  conducted  from 
the  red  portion  to  the  point,  than  it  radiates  to  the  air,  and 
the  first  heat  to  the  edge  only  gives  a  yellow;  with  more,  it 
becomes  purple,  and  so  on.  Hardened  drill  and  pick  points 
are  treated  in  in  this  way,  4"  of  the  end  being  heated  to  a 
yellow;  and,  in  thirds,  the  tempering  is  proceeded  with  as 
above. 


''i 


H 


)  ! 

!i 


198 

"Care  should  be  taken  that  the  plunged  too!  while  temper- 
ing, be  not  held  too  long  a  time  at  a  certain  color  line,  as  it 
has  a  tendency  to  break  at  that  point.  The  tool  should  be 
slightly  waved  in  the  water.  '  Pieces  '  which  are  to  be  tem- 
pered throughout  must  be  allowed  to  soak,  /.  <'.,  become 
uniformly  hot.  before  plunging. 

"The  proper  color  for  a  given  ground,  is  only  ascertained 
by  experience.  Generally  speaking,  the  picks  and  drills  are 
stopped  at  a  '  straw,'  if  intended  for  hard  ground  ;  at  a  blue, 
for  mild  ground.  The  toughness  of  the  steel  should  be  pre- 
served as  much  as  possible,  therefore  select  the  lowest  color 
Compatible  with  the  service  to  be  performed.  A  high  carbon 
steel  is  given  a  lighter  color  than  steel  of  low  carbon. 

"A  pick  is  made  of  a  square  iron  b«ir  14"  x  iX"  heated  at 
the  middle,  and  then  struck  endwise,  till  about  i>^"  across. 
This  spot  is  softened  and  at  red  heat,  cut  open,  and  swelled 
by  a  drift  to  form  the  eye.  This  is  then  slit  at  the  ends,  and 
softened,  while  a  6"  length  t)f  pick  steel  is  being  heated. 
When  ready,  this  steel  is  tongued  into  the  iron,  and  ham- 
mered. A  reheating  with  borax,  and  a  hammering  complete 
the  weld,  after  which  the  picks  are  sharpened  and  tempered, 
no  signs  of  the  weld  should  be  visible." 

"  Pick-steel  "  is  a  special  steel  that  can  be  had  in  bars  i^" 
or  1^"  X  ^"  or  |^"and  used  only  ff)r  tips. 

Steel  bars  for  drills  come  in  lengths  of  about  14  feet  each 
and  from  ^"  to  2"  diameter.  The  American  "Black  Dia- 
mond "  brand  is  a  favorite.  The  bars  are  cut  into  pieces  as 
long  as  can  conveniently  be  used,  e.jf.  30"  and  36".  The  bits 
are  wider  than  the  tool,  to  prevent  it  sticking  to  the  hole. 
The}'^  are  widened  according  to  pattern,  so  they  can  "  follow  " 
well.  The  first  drill  has  the  widest  bit;  the  followers  nar- 
rower ones.  In  hard  rock  the  flare  is  smaller  than  that  in 
soft  rock. 

"The  temper  is  a  lighter  color  for  hard  than  for  soft  rock. 
If  the  edges  of  the  returned  drills  are  cracked  or  broken  the 
steel  is  too  brittle,  and  should  be  made  softer  or  other  coal 
used.  If  the  edges  blunt  much  by  wearing  round,  they  are 
all  right,  though  a  harder  temperature  may  give  them  longer 
life.  Cast  steel  borers  are  never  heated  above  a  cherry. 
They  are  annealed  at  the  striking  end." 

PRACTICAL    SUGGESTIONS    AND    POINTS     BY    A    BLACKSMITH. 

A  prospector  must  have  something  to  act  as  an  anvil,  a 
hard  pebble  wont  do,  he  can  carry  a  small  anvil  or  a  chunk 


199 


of  railroad  iron.  A  small  iiand  bellows  or  even  a  portable 
forge  worked  witb  a  crank  will  make  bis  cnittit  complete. 
The  followinfj;  practical  bints  I  picked  up  from  a  blacksmith 
whilst  watchinp^  him  at  work  tempering  both  picks  and 
drills  for  some  prospectors.  He  said:  "  Vou  must  temper 
your  drill  according  to  the  character  of  the  rocks. 

"For  hard  rock,  use  a  short  thick  edged  'bull  bit'  which 
will  stand  a  high  brittle  temper  such  as  '  straw.'  For  picks, 
a  light  blue  color  is  a  good  temper,  rather  than  '  straw  'which 
is  too  brittle.  Cherry  red  is  the  heat  of  your  bar,  not  hotter  ; 
laying  this  on  the  anvil  and  hammering  it  well  all  over  gives 
it  toughness.  If  blisters  show  on  the  steel  you  must  hammer 
it  over  again.  By  occasionally  dipping  your  hammer  in 
water  and  then  striking  with  it,  you  get  the  steel  down  to  a 
fine  grain.  When  you  are  dipping  for  tempering,  put  the 
point  in  the  water,  that  cools  the  point,  and  the  heat  runs 
the  color  down  to  the  cool  point ;  when  the  color  reaches  the 
tint  you  want,  then  is  your  time  to  cool  off  quickly.  The 
color  progresses  from  a  white  or  pale  straw  to  copper  color, 
to  blue.  Copper  tint  is  a  good  one  to  stop  at  for  a  drill, — 
blue,  for  a  pick.  The  right  moment  to  stop  and  cool  is  just 
at  the  turning  point  from  one  color  to  another." 

He  took  a  piece  of  steel,  heated  it  to  cherry  red,  laid  it  on 
the  anvil  and  pounded  it  lightly  with  his  hammer  all  over,  to 
toughen  it  by  blows,  occasionally  dipping  his  hammer  in  the 
water  to  "  water  temper"  it :  this  further  toughens  it,  by  par- 
tially cooling  it.  Now  the  bar  was  again  put  in  the  fire  and 
heated  to  a  cherry  red,  care  being  taken  not  to  keep  the  bar 
too  long  in  the  fire,  as  that  would  tend  to  take  its  toughness 
out,  or  produce  blisters.  The  bar  was  plunged  about  an  inch 
into  the  water,  and  then  rubbed  against  a  brick,  to  show  the 
colors  plainer.  These  passed  from  the  point  upwards,  gradu- 
ally through  the  colors  we  have  mentioned  ;  to  arrest  it  by 
suddenly  cooling  off  at  "  straw,''  would  make  it  too  brittle 
for  ordinary  drills,  except  a  "  bull  drill."  Now  the  "  straw  " 
turns  into  a  copper  hue,  a  good  point  to  cool  off  for  a  d^r///. 
Now  it  passes  into  a  blue,  at  this  point  it  would  be  well  to 
cool  off  for  -dipick.  The  edge  of  a  drill  is  almost  of  second- 
ary importance  to  the  sharpness  of  the  projecting  corners : 
when  these  are  gone,  the  drill  is  used  up,  and  clogs  in  the 
hole.  Some  rocks  like  sandstone  will,  by  reason  of  the 
quartz  in  them,  wear  off  the  corners  very  rapidly,  others,  like 
limestone  or  granite,  less  rapidly. 

Another  blacksmith  advised  me  not  to  dip  (as  is  commonly 
done)  the  point  only  an  inch  in  water  as  it  is  apt  in  use  to 


300 


break  at  the  water  line,  but  phinj?e  it  all  oyer  in  the  water. 
"  Who  shall  flocific  when  doctors  disagree  ?  " 

A  prospector  should  take  with  him  a  rejrular  bhu:ksniith's 


hammer  tor  sharneniufr,  as  well  as  the  4  or  5-lb.  hammer  he 
uses  tor  striking  drill  or  the  rock. 


CHAPTER  XVI. 

SOME     ELEMENTS     OF     MINING     LAW     RELATING     TO 

PROSPECTING. 

A  prospectt^r  would  do  well  to  actiuaint  himself  with  a  few 
elements  of  mining  law,  so  we  will  give  a  few  samples  <jf 
Colorado  mining  law  for  his  benefit. 

l-lxfent  of  Lode  or  Claim. — The  length  of  any  lode  may 
equal,  but  not  exceed,  1,500  feet  along  t!ie  vein. 

Dimensions. — The  width  of  lode  claims  in  Gilpin,  Clear 
Creek,  Boulder  and  Summit  counties,  shall  be  75  feet  on  each 
side  of  the  center  of  the  vein  or  cre\'ice. 

Certificate  of  Location. — The  discoverer  of  a  lode  shall, 
within  three  months  from  the  date  of  discovery,  record  his 
claim  in  the  office  of  the  recorder  of  the  county  in  which 
such  lode  is  situated,  by  rt  location  certificate,  which  shall 
contain  : 

1st.    The  name  of  the  lode.    ..,.',,  ' 

2d.     The  name  of  the  locator.. "' r" 
3d.     The  date  of  the  location. 

4th.  The  number  of  feet  in  length  claimed  on  each  side  of 
the  center  of  the  discovery  shaft. 

5th.  The  general  course  of  the  lode  as  near  as  may  be. 

Discovery  Shaft. —  Before  filing  such  location  certificate, 
the  discoverer  shall  locate  his  claim  by  first  sinking  a  dis- 
covery shaft  on  the  lode,  to  the  depth  of  at  least  10  feet,  or 
deeper  if  necessary,  to  show  a  well-defined  crevice. 

Second,  by  posting  at  the  point  of  disccjvery  on  the  sur- 
face, a  plain  sign  or  notice  containing  the  nrtme  of  the 
lode,  the  name  of  the  locator  and  the  date  of  the  discovery. 

Third,  by  marking  the  surface  boundary  line  of  the  claim. 


20I 


.S/<//7;/i,'.— Such  surface  boundaries  shall  he  marked  by 
six  substantial  posts,  hewed  or  marked  on  the  side  or  sides 
of  which  are  in  toward  the  claim,  and  sunk  in  the  j^round, 
to  wit,  one  at  each  corner,  anfl  one  at  the  center  of  each  side 
line.  Where  it  is  "inpossible  on  account  of  bed  rock,  or  pre- 
cipitous j^round,  to  sink  such  posts,  they  may  be  placed  in  a 
pile  of  stones. 

Open  Cuts. — Any  open  cut  or  cross-cut  tunnel,  or  tunnel 
which  shall  cut  a  lode  at  the  depth  of  ten  feet  below  the  sur- 
face, shall  hold  it,  the  same  as  if  a  discovery  shaft  were  sunk 
thereon,  or  an  adit  of  at  least  ten  feet  along  the  lode  from 
the  noin+  where  the  lode  may  be  in  any  manner  discovered, 
shall  be  equi\alent  to  a  discovery  shaft. 

'rime. — The  discoverer  shall  have  60  days  from  the  time 
of  uncovering  or  disclosing  a  lode,  to  sink  a  discovery  shaft 
thereon. 


'Construction  of  Certifuixtc. — The  location  certificate  of  any 
le  claim  shall  be  constructed  to  include  all  surface  ground 


lodes  and  ledges 


C 
lod 

within  the  surface  lines  thereof,  and  ai 
throughout  their  entire  depth,  the  top  or  "apex  "  of  which 
lies  inside  of  such  lines  extending  downward  vertically,  with 
such  parts  of  all  lodes  or  ledges  as  C(-)ntinue  to  dip  beyond 
the  side-lines  of  the  plane,  but  shall  not  include  any  portion 
of  such  lodes  or  ledges  beyond  the  end  lines  of  the  claim,  or 
at  the  end-lines  continued,  whether  by  dip  or  otherwise,  or 
beyond  the  sioe-lines  in  any  other  manner  than  by  the  dip 
of  the  lode. 

Cannot  be  Followed. — If  the  top  or  "apex  "  of  a  lode  in  its 
longitudinal  course  extends  beyond  the  exterior  lines  of  the 
claim  at  any  point  on  the  surface,  or  as  extended  vertically 
downward,  such  lode  may  not  be  followed  in  its  longitudinal 
course  beyond  the  point  where  it  is  intersected  by  the  ex- 
terior lines. 

Proof  of  De^u'lopmcnt. — The  amount  of  work  done,  or  im- 
provements made  during  each  year  shall  be  that  prescribed 
by  laws  of  the  United  States. 

Placer  Mining  Claims, — The  discoverer  of  a  placer  claim 
shall,  within  30  days  from  the  date  of  discovery,  record  his 
claim  in  the  office  of  the  recorder  of  the  county  in  which 
said  claim  is  situated,  by  a  location  certificate,  which  shall 
contain  : 

I  St.  The  name  of  the  claim,  designating  it  as  a  placer 
claim. 


202 


2(].     The  name  of  the  locator. 

3(1.     The  date  of  the  location. 

4th.   The  miniher  oi  feet  or  acres  claimed. 

5th.  The  descrijUion  of  the  claim  hy  such  reference  to 
natural  objects  or  permanent  moiniments  as  shall  identify 
the  claim. 

Befcjre  filinjif  such  hjcation  certificate,  the  discover  shall 
locate  his  claim  ; 

1st.  By  postin/j;  upon  such  claim  a  plain  sijj;n  or  notice 
containinjj;  the  name  of  the  claim  and  of  the  locator,  the 
date  of  discovery,  and  number  of  acres  or  feet  claimed. 

2d.  ]\y  nnwkiufr  the  surface  boundaries  with  substantial 
posts  sunk  in  the  fi;round,  one  at  each  anj.>;le  of  the  claim. 

On  each  placer  claim  of  i6o  acres,  not  less  than  loo  dollars' 
worth  of  labor  shall  be  done  by  the  first  of  Auf>^ust  each 
year,  and  upon  less  or  more  ground  a  sum  in  pr(jportion. 


I  TsT  D  i:  X  . 


Algonkian  Epoch 26-27 

Alteration  of  Rocks  and  Ores gy,  161 

Andesite  Lava 23,  35,  57,  94,  124,  127,  137,  141,  151 

Apex  and  Side  Line 171,  172 

Archaean  Age 18,  20,  21,  39.  96 

Argentitc  Ore 63 

Arizona 95 

Aspen  Mining  Camp 75,  83,  85,  88,  99,  165--174 

Augite 51 

Australia io(\  1 10 

Manded  or  Ribbon  Structure 87 

Barite 52,  76,  161 

Basalt  Lava 34,  35,  57,  58,  94,  112 

Beach  Mining  , 113 

Bismulhinite  Ore 62,  95 

Blanket  Deposits 73,  75,  151 

"  Blossom  •'  Rock 88,  171 

"Blue  Lead" 112 

"  Blue  Limestone  " .22,  39,  156 

"  Booming  "  Mines 173 

Boulder  Mining  Region 20,  26,  73,  93,  117-123 

Bowen  Mine 88 

Calcite 51 

California.. 34,  105,  iii,  112,  113,  115 

Cambrian 21,  28,  40,  48 

Canyons 19,  20,  35 

Carbonates 65,  66 

Carboniferous 18,  21,  31,  42,  43,  49,  156,  168 

Caves  and  Cavities 162,  163,  169 

Chlorides 64 

Chlorite 51 

Cinnabar 35.  132 

Coal - 23,  31 

Comstock  Mine ..8,  92,  103,  no 

Contact  Ore  Deposits 49,  73,  94,  151,  169 

Copper 60,  61,  65,  126 

Country  Rock 97 

Creed  Mining  Camp 126 

Cretaceous 23,  33,  45,  9^ 

Cripple  Creek  Mining  Region      12,35,94,  128-151 

Cross  Cutting loi,  102 


204 


INDKX. 


PACE 

Cross  Veins •   -86,  87 

Dakotah  Group - - 23 

Decomposed  Ores ■-   --   92 

Dendrite 147 

Deep  Leads - .rii 

Devonian - - 30.  42 

Dinosaurs - 23,  32 

Diorite 55.  94.  1 68 

Dip --- 85,  loi,  102 

Dolomite -- - 21,51 

Dolomitization..i. _ 75,  170 

Drilling -  - 76,  195 

Dykes 50,93,94,100,130,149,   154 

Earth's  Origin — .25 

Ed ucation  of  Prospector. — - 8 

Effusive   Rocks - - 57 

Eruptive  Rocks     , 57,94,98 

Eureka  Mines -    30 

Examining  Mines — 174-185 

Faults 68-71,  79,  80,  81,  93.  153 

Feldspar —  50 

Fissure  Veins 48,  77,  87,  90.  117,  123,  131 

"Float  " - 13,  14.  88,  144,  145,  147 

Folds 28,68,81 

Fossils - 23,  29,  30,  32,  33,  34.  38--46 

Free  Milling  Ore 88,  95,  iSi 

Galena - 8,  98,  156,  161,  181 

Gases -139 

Geography,  Ancient 29,  33 

Geology,  Historical 24-46 

Geological  Ages 20,  23 

Geological  Sections 17-19 

Geological  Training 15 

Geological  Works -I5 

Glacial  Action ._  116,  156 

Glacial  Epoch 35 

Gneiss 53.  54 

Gold.- 18,  21,  28,  32,  34,  35,  61,  98,  104-111,  114,  181 

Gouge 85 

Grand   Canyon 19 

Granite 52 

Grits  (Weber) _ 22,  31 

Gunnison  Region 96 

Gypsum 52 

Historical  Geology. r-24 

Hornblende , 51 

Horses :7s 

Hydraulics.. 113 

Igneous  Rocks ^. ....... .54,  72 


INDEX. 


205 


Impregnations 82,  86,  145,  164 

Indications 78,  79.  M3.  '44 

Intrusive  Rocks... - 54-  72,  94 

Joints • 69-71,  82 

Jurassic -25,44 

kaolin i<Ji 

Kootanie   Region 27 

Laccolites -54 

Laramie  Group. --- 23,  32,  33,  46 


Lateral  Secretion' 


98 


Lavas 23,  35,  94,  98.  134-  136,  I37.  142 

Leadville  22,  32,  38,  55,  56,  85,  94,  95,  99,  100,  114,  156-163 

Limestone - --i8,  22,28,  98,  100 

Lincoln  Mt ---- - 20,  IT7.  153 

Lithology - --- 47 

"  Loaming". - - 108,  109 

Locating - ----14.  172,  I73,  200-201 

M amm oth - -  24,  46 

Manitou ^9 

Manganese - - 59'   ^"O 

Mesozoic,  Meaning  of 34 

Metasomatic  Replacement 74.  97>  162,  165 

Mica -- 51 

Microscopy  of  Minerals I33"i35 

Mineralogy - - 59 

Minerals - 50,  51,  59.  62,  63,  64-67,  t6i 

Mineral  Waters - - 69,  70 

Mining  Laws - .200-201 

Mosquito  Range - - ^57 

Nebular  Theory 25 

Nuggets ii»  95.  105.  106,  III,  164 

Obsidian - - - -  -  -  58 

Openings  in  Rocks '         V 

Ore  Chimneys ^^4 

Ore  Deposits-.-.. -. --67,  74,  75-  83,  94.  159-  i^o 

Outcrop - - •  ^^ 

Outfit - 9 

Paleozoic,  Meaning  of -  -  - -  -32 

Paleontology - - -  -  3o.  39 

Panning --- --   i^-  ^3.  H 

Pay  Streak '^^ 

Phonolite ^37.  142 

Placers. n.  13,35,36,  104-11J,  114.  2or 

Pockets 9^ 

Polybasite - - ^3 

Porphyry.. 21,  50,  55,  56,94.  i34.  I54.  168 


Pre-Cambrian 


.26 


Pvrites  - 62,  88.  181 

Quartz 50.181 


2o6  INDEX. 

PAGE 

Quartz  Porphyry.. 55,  56.  57.  121,  154 

Quartzite 18,  21,  22,  28,  53,  163 

Quaternary . 23,  35 

Recent  Disturbances - —  36 

Red  Cliff  Mines 28,  62,  163,  164 

Rhyolite 23,  35.  57,  94-  151 

Richness  with  Depth 91,  92,  148,  171 

Rocks 47,  50,  123 

Rosita  Mines 127 

Ruby  Silver 61,64 

Saltinji  ivlines 178,  185-192 

Sampling  Mines 179,  188 

Sandstones 18,  21.  98 

San  Juan  Mining  Region 35,  78,  87-S9,  95,  97,  99,  .05 

124-127,  176,  177 

Schists - 53 

Sedimentary  Rocks 48,151 

Serpentine - - 54 

Sharpening  Tools 196 

Siderite  Iron 60 

Silurian 21,  28,  41,  48 

Silver  Cliff  Mines 35,  127 

Silver  Reef  Sandstone 33,  82 

Soifataric  Action 139,  140 

Solutions 67-73,  97,  99,  100,  104,  125,  138,  169 

South  Park  Mining  Region 20,  49,  81,  116,  151-156 

Steamboat  Springs 140 

Stephanite 63 

Strike 85,  101-102 

Stromboli  Volcano -128 

Surface  Ores 95,  147,  148,  1 74 

Surface  Signs - 75.  79 

Syenite 53 

Talc , - - 51,  161 

Tellurides ..i  18-122 

Tempering  Steel 197-199 

Tertiary 23,  34,  97,  124 

Tin  Ore 30,  97 

Tools 10,  192 

Trachyte   Lava 58 

Triassic 22,  32,  44 

Tunnels 102 

Unconformity 30 

Veins 21,  48,  77,  84.  86,  87 

Vesuvius  Volcano 131 

Volcanic  Action---.34,  35,  93,  127,  128,  131,  135,  141,  151,  153,  155 

Walls 85,  86,  150 

Weber  Canyon 19 

Zinc. 21,  66,  126,  156,  160 


LIST   OF   AUTHORS. 


207 


LIST     OF     AUTHORS     AND     WORKS 
REFERRED     TO. 


Balch,  W.  R.  }  Mines,  Miners  and  Mining  Interests  of  the  United 

Balch,  A.         )      States. 

Cross,  Whitman. — Geology  of  Cripple  Creek. 

Dana,  J.  D. — Geology  and  Mineralogy. 

Emmons,  S.  F. — Geology  and  Mining  Industry  of  Leadville. 

Parish,  J.  B. — A  Typical  Boulder  County  Mine. 

Geikie,  A. — Hand  Book  of  Field  Geology. 

Guiterman,  F. — Red  Cliff  Gold  Deposits. 

Ihlseng,  M.  C. — Manual  of  Mining. 

Judd,  J.  W. — Volcanoes. 

Kemp,  J.  F. — Ore  Deposits. 

Lakes,  A. — Geology  of  Colorado  and  VVestem  Ore  Deposits. 

Le  Conte,  J. — Geology. 

Lock,  A.  G.— Gold,  its  Occurrence  and  Extraction, 

Lock,  C.  G.  W.— Practical  Gold  Mining. 

Penrose,  Arthur. — Ore  Deposits  of  Cripple  Creek. 

Phillips,  J.  A. — Ore  Deposits. 

Williams,  Albert,  Jr.— Mineral  Resources  of  the  United  States. 


